TRẦN MINH TƯỜNG

<h2 class="sub-title">Giải Toán 8 Bài tập cuối chương 5 - Chân trời sáng tạo</h2>
Bài 2 trang 28 Toán 8 Tập 2: Độ dài cạnh MN của tứ giác trong câu 1 là:

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A. 3;
B. 5;
C. <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>3</mn></msqrt></math>;
D. <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>5</mn></msqrt></math> .
Lời giải: 
<img alt="Bài 2 trang 28 Toán 8 Tập 2 Chân trời sáng tạo | Giải Toán 8" src="../toan-8-ct/images/bai-2-trang-28-toan-lop-8-tap-2.PNG" />

Đáp án đúng là: A
Từ đồ thị hàm số ta có MN = 3.

Giải Toán 8 Bài tập cuối chương 5 - Chân trời sáng tạo Bài 2 trang 28 Toán 8 Tập 2: Độ dài cạnh MN của tứ giác trong câu 1 là: Quảng cáo ...

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Lý thuyết Giải hệ hai phương trình bậc nhất hai ẩn Toán 9

1. Cách giải hệ phương trình bằng phương pháp thế<table border="0" cellpadding="0" cellspacing="0" style="background-color: #deebf7;">
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Bước 1. Từ một phương trình của hệ, biểu diễn một ẩn theo ẩn kia rồi thế vào phương trình còn lại của hệ để nhận được một phương trình một ẩn.
Bước 2. Giải phương trình một ẩn đó rồi suy ra nghiệm của hệ.
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</table>Ví dụ:1. Hệ phương trình \(\left\{ \begin{array}{l}2x - y = 3\\x + 2y = 4\end{array} \right.\) được giải bằng phương pháp thế như sau:Từ phương trình thứ nhất của hệ, ta có \(y = 2x - 3\).Thế vào phương trình thứ hai của hệ, ta được \(x + 2\left( {2x - 3} \right) = 4\) hay \(5x - 6 = 4\), suy ra \(x = 2\).Từ đó \(y = 2.2 - 3 = 1\).Vậy hệ phương trình đã cho có nghiệm là \(\left( {2;1} \right)\).2. Hệ phương trình \(\left\{ \begin{array}{l}x - y = - 2\\2x - 2y = 8\end{array} \right.\) được giải bằng phương pháp thế như sau:Từ phương trình thứ nhất của hệ, ta có \(x = y - 2\).Thế vào phương trình thứ hai của hệ, ta được \(2\left( {y - 2} \right) - 2y = 8\) hay \(0y - 4 = 8\).Do không có giá trị vào của y thỏa mãn hệ thức \(0y - 4 = 8\) nên hệ phương trình vô nghiệm.3. Hệ phương trình \(\left\{ \begin{array}{l} - x + y = - 2\\3x - 3y = 6\end{array} \right.\) được giải bằng phương pháp thế như sau:Từ phương trình thứ nhất của hệ, ta có \(y = x - 2\).Thế vào phương trình thứ hai của hệ, ta được \(3x - 3\left( {x - 2} \right) = 6\) hay \(0x = 0\).Ta thấy mọi giá trị của x đều thỏa mãn \(0x = 0\).Với giá trị tùy ý của x, giá trị tương ứng của y được tính bởi \(y = x - 2\).Vậy hệ phương trình có nghiệm là \(\left( {x;x - 2} \right)\) với \(x \in \mathbb{R}\) tùy ý.2. Cách giải hệ phương trình bằng phương pháp cộng đại số:<table border="0" cellpadding="0" cellspacing="0" style="background-color: #deebf7;">
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Bước 1. Nhân hai vế của mỗi phương trình với một số thích hợp (nếu cần) sao cho các hệ số của một ẩn nào đó trong hai phương trình của hệ bằng nhau hoặc đối nhau.
Bước 2. Cộng hay trừ từng vế của hai phương trình trong hệ để được một phương trình một ẩn và giải phương trình đó.
Bước 3. Thế giá trị của ẩn tìm được ở Bước 2 vào một trong hai phương trình của hệ đã cho để tìm giá trị của ẩn còn lại. Kết luận nghiệm của hệ.
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</table>Ví dụ:1. Hệ phương trình \(\left\{ \begin{array}{l}5x - 7y = 9\\5x - 3y = 1\end{array} \right.\) được giải bằng phương pháp cộng đại số như sau:Trừ từng vế hai phương trình ta được \(\left( {5x - 5x} \right) + \left( { - 7y + 3y} \right) = 9 - 1\) hay \( - 4y = 8\), suy ra \(y = - 2\).Thế \(y = - 2\) vào phương trình thứ hai ta được \(5x - 7.\left( { - 2} \right) = 9\) hay \(5x + 14 = 9\), suy ra \(x = - 1\).Vậy hệ phương trình đã cho có nghiệm duy nhất là (-1;-2).2. Hệ phương trình \(\left\{ \begin{array}{l}3x - 5y = 2\\ - 6x + 10y = - 4\end{array} \right.\) được giải bằng phương pháp cộng đại số như sau:Chia hai vế của phương trình thứ hai cho 2, ta được hệ \(\left\{ \begin{array}{l}3x - 5y = 2\\ - 3x + 5y = - 2\end{array} \right.\)Cộng từng vế hai phương trình của hệ mới ta có \(0x + 0y = 0\). Hệ này luôn thỏa mãn với các giá trị tùy ý của x và y.Với giá trị tùy ý của x, giá trị của y được tính nhờ hệ thức \(3x - 5y = 2\), suy ra \(y = \frac{3}{5}x - \frac{2}{5}\).Vậy hệ phương trình đã cho cho nghiệm là \(\left( {x;\frac{3}{5}x - \frac{2}{5}} \right)\) với \(x \in \mathbb{R}\).3. Cách tìm nghiệm của hệ hai phương trình bằng máy tính cầm tay<table border="0" cellpadding="0" cellspacing="0" style="background-color: #deebf7;">
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Ta sử dụng loại máy tính cầm tay (MTCT) có chức năng này (có phím MODE/MENU). Dưới đây là hướng dẫn cụ thể với máy Fx-580VNX.
Ta viết phương trình cần giải dưới dạng \(\left\{ \begin{array}{l}{a_1}x + {b_1}y = {c_1}\\{a_2}x + {b_2}y + {c_2}\end{array} \right.\).
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</table>Ví dụ: Giải hệ \(\left\{ \begin{array}{l}2x + y - 4 = 0\\ - 2x + y = 0\end{array} \right.\), ta viết nó dưới dạng \(\left\{ \begin{array}{l}2x + y = 4\\ - 2x + y = 0\end{array} \right.\).Khi đó, ta có \({a_1} = 2\), \({b_1} = 1\), \({c_1} = 4\), \({a_2} = - 2\), \({b_2} = 1\), \({c_2} = 0\). Lần lượt thực hiện các bước sau:Bước 1. Vào chức năng hệ hai phương trình bậc nhất hai ẩn bằng cách nhấn MENU rồi bấm phím 9 để chọn tính năng Equation/Func (Ptrình/HệPtrình).<img src="https://img.loigiaihay.com/picture/2024/0627/1_3.png" />Bấm phím 1 để chọn Simul Equation (hệ phương trình).<img src="https://img.loigiaihay.com/picture/2024/0627/1_4.png" />Cuối cùng, bấm phím 2 để giải hệ hai phương trình bậc nhất<img src="https://img.loigiaihay.com/picture/2024/0627/1_5.png" />Bước 2. Ta nhập các hệ số \({a_1},{b_1},{c_1},{a_2},{b_2},{c_2}\) bằng cách bấm<img src="https://img.loigiaihay.com/picture/2024/0627/1_6.png" />Bước 3. Sau khi nhập xong, ta bấm phím =, màn hình hiện x = 1; tiếp tục bấm =, màn hình hiện y = 3. Ta hiểu nghiệm của hệ phương trình là (-1;2).Chú ý:- Muốn xóa số vừa mới nhập thì bấm phím AC, muốn thay đổi số đã nhập ở vị trí nào đó thì di chuyển con trỏ đến vị trí đó rồi nhập số mới.- Bấm phím ▲ hay ▼ để chuyển hiển thị các giá trị của x và y trong kết quả.- Nếu máy báo Infinite Solution thì hệ phương trình đã cho có vô số nghiệm.Nếu máy báo No Solution thì hệ phương trình đã cho vô nghiệm.4. Giải bài toán bằng cách lập hệ phương trìnhCác bước giải bài toán bằng cách lập hệ phương trình:<table border="0" cellpadding="0" cellspacing="0" style="background-color: #deebf7;">
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Bước 1. Lập hệ phương trình:
- Chọn hai ẩn biểu thị hai đại lượng chưa biết và đặt điều kiện thích hợp cho các ẩn số;
- Biểu diễn các đại lượng liên quan theo các ẩn và các đại lượng đã biết;
- Lập hệ hai phương trình bậc nhất hai ẩn biểu thị mối quan hệ giữa các đại lượng.
Bước 2. Giải hệ phương trình nhận được.
Bước 3. Kiểm tra nghiệm tìm được ở bước 2 có thỏa mãn điều kiện của ẩn hay không, rồi trả lời bài toán.
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</table>Ví dụ 1: Giải bài toán bằng cách lập hệ phương trìnhHai xe cùng khởi hành một lúc ở hai tỉnh A và tỉnh B cách nhau 60km. Nếu đi ngược chiều thì gặp nhau sau 1 giờ; nếu đi cùng chiều thì xe đi nhanh sẽ đuổi kịp xe kia sau 3 giờ. Tìm vận tốc mỗi xe.Lời giải:Gọi x là vận tốc của xe đi nhanh, y là vận tốc của xe đi chậm ( \(x,y > 0;x > y\) và x, y tính bằng km/h).Sau 1 giờ hai xe gặp nhau, nên ta có phương trình:x + y = 60Sau 3 giờ mỗi xe đi được 3x; 3y ( km) và gặp nhau, nên ta có phương trình:3x – 3y = 60.Vậy, ta có hệ phương trình:\(\begin{array}{l}\left\{ \begin{array}{l}x + y = 60\\3x - 3y = 60\end{array} \right.\\\left\{ \begin{array}{l}3x + 3y = 180\\3x - 3y = 60\end{array} \right.\end{array}\)\(\left\{ \begin{array}{l}x = 40\\y = 20\end{array} \right.\)(\(x = 40;y = 20\) thỏa mãn các điều kiện đã nêu)Vậy xe đi nhanh có vận tốc \(40\;(km/h)\), xe đi chậm có vận tốc \(20\;(km/h)\).Ví dụ 2: Giải bài toán bằng cách lập hệ phương trìnhTìm một số có hai chữ số, biết rằng tổng của hai chữ số ấy bằng 12 và khi thay đổi thứ tự hai chữ số thì được một số lớn hơn số cũ là 18.Lời giải:Gọi x, y là các chữ số hàng chục và hàng đơn vị của số đã cho (\(x \in \mathbb{N}\),\(0 < x \le 9\) ,\(0 \le x \le 9\))Khi đó hai số có dạng \(\overline {xy} = 10x + y\) và \(\overline {yx} = 10y + x.\)Ta có hệ phương trình:\(\left\{ \begin{array}{l}x + y = 12\\10y + x - 18 = 10x + y\end{array} \right.\)\(\left\{ \begin{array}{l}x + y = 12\\x - y = 2\end{array} \right.\)\(\left\{ \begin{array}{l}x = 5\\y = 7\end{array} \right.\)Vậy số cần tìm là 57.

Lý thuyết Giải hệ hai phương trình bậc nhất hai ẩn Toán 9

1. Cách giải hệ phương trình bằng phương pháp thế Bước 1. Từ một phương trình của hệ, biểu diễn một ẩn theo ẩn kia rồi thế vào phương...

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<div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">
<p align="center" style="background-color: white; box-sizing: border-box; color: #222222; font-family: Roboto, sans-serif; font-size: 16px; line-height: 24px; margin-bottom: 1rem !important; margin-left: 0px !important; margin-right: 0px !important; margin-top: 0px; margin: 0px 0px 1rem; word-break: break-word;">Trắc nghiệm Toán 8 Bài 1: Định lí Pythagore<div class="question c64a930eaefb726e3b384dab4" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;"><div class="question c64a930ebefb726e3b384dac0" style="border-bottom: none; box-sizing: border-box; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%; text-align: inherit;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 1 : Tam giác ABC có AB = 3 cm, AC = 4cm, BC = 5cm. Tam giác ABC là tam giác gì?</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác nhọn</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác tù.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác vuông.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Không đủ dữ kiện để xác định</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : C<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải:</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>3</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>25</mn></mtd></mtr><mtr><mtd><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>5</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>25</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></mtd></mtr></mtable></math>" id="MathJax-Element-1-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=32+42=25<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=52=25⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>3</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>25</mn></mtd></mtr><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>5</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>25</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mtd></mtr></mtable></math>Vậy tam giác ABC là tam giác vuông</div></div></div></div><div class="question c64a930ebefb726e3b384dac6" style="border-bottom: none; box-sizing: border-box; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%; text-align: inherit;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 2 : Cạnh huyền của một tam giác là bao nhiêu biết hai cạnh góc vuông là 3 và 4.</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">8</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">7</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">6</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">5</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Đáp án : D<div class="solution-detail" style="box-sizing: border-box; font-size: 16px; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải:</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Độ dài cạnh huyền là: <msqrt><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>3</mn><mn>2</mn></msup></mrow></msqrt><mo>=</mo><mn>5</mn></math>" id="MathJax-Element-2-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">√42+32=5<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>3</mn><mn>2</mn></msup></mrow></msqrt><mo>=</mo><mn>5</mn></math></div></div></div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;"> </div></div>Câu 3: Lựa chọn  phương án đúng nhất:</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Nếu một tam giác có bình phương của một cạnh bằng tổng các bình phương của hai cạnh kia thì tam giác đó là tam giác nhọn.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Nếu một tam giác có bình phương của một cạnh bằng tổng các bình phương của hai cạnh kia thì tam giác đó là tam giác vuông.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Nếu một tam giác có bình phương của một cạnh bằng tổng các bình phương của hai cạnh kia thì tam giác đó là tam giác tù.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Nếu một tam giác có bình phương của một cạnh bằng tổng các bình phương của hai cạnh kia thì tam giác đó là tam giác cân.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : B<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải:</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Ta có định lí Pythagore đảo: Nếu một tam giác có bình phương của một cạnh bằng tổng các bình phương của hai cạnh kia thì tam giác đó là tam giác vuông.</div></div></div></div><div class="question c64a930ebefb726e3b384daba" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 4 : Cho tam giác ABC vuông tại B, khi đó:</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-3-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math></div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-4-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math></div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-5-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math>.  </div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-6-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math></div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : A<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải:</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Vì tam giác ABC vuông tại B nên theo định lý Pythagore ta có <mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-7-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math>.</div></div></div></div><div class="question c64a930ebefb726e3b384dac0" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 5 : Cho tam giác ABC cân tại A. Kẻ AH  vuông góc với BC tại H. Cho BH = 2cm, AB = 4cm. Tính AH:</div></div></div><div class="question c64a930ebefb726e3b384dad8" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><msqrt><mn>10</mn></msqrt><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-8-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">√10<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>10</mn></msqrt><mi>�</mi><mi>�</mi></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><msqrt><mn>13</mn></msqrt><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-9-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">√13<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>13</mn></msqrt><mi>�</mi><mi>�</mi></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><msqrt><mn>12</mn></msqrt><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-10-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">√12<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>12</mn></msqrt><mi>�</mi><mi>�</mi></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">12 cm.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : C<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><img alt="" height="149" src="https://tailieumoi.vn/storage/uploads/images/74117/17-1703747756.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="225" />Áp dụng định lí Pythagore cho <mi mathvariant="normal">&#x394;</mi><mi>A</mi><mi>B</mi><mi>H</mi></math>" id="MathJax-Element-11-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">Δ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Δ</mi><mi>�</mi><mi>�</mi><mi>�</mi></math> vuông tại H ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>2</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>12</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mi>H</mi><mo>=</mo><msqrt><mn>12</mn></msqrt><mi>c</mi><mi>m</mi></mtd></mtr></mtable></math>" id="MathJax-Element-12-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=42−22=12⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H=√12<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>2</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>12</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>12</mn></msqrt><mi>�</mi><mi>�</mi></mtd></mtr></mtable></math>Vậy <mi>A</mi><mi>H</mi><mo>=</mo><msqrt><mn>12</mn></msqrt><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-13-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H=√12<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>12</mn></msqrt><mi>�</mi><mi>�</mi></math></div></div></div></div><div class="question c64a930ebefb726e3b384dade" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;"><div class="question c64a92e9defb726e3b384da78" style="border-bottom: none; box-sizing: border-box; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%; text-align: inherit;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 6 : Chọn phát biểu đúng nhất về định lí Pythagore:</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Trong một tam giác vuông, bình phương cạnh huyền bằng tổng bình phương hai cạnh góc vuông.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Trong một tam giác vuông, cạnh huyền bằng cạnh góc vuông.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Trong tam giác vuông, bình phương cạnh huyền bằng bình phương cạnh góc vuông.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Trong một tam giác vuông, bình phương cạnh huyền bằng tổng hai cạnh góc vuông.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : A<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Định lí Pythagore phát biểu là: Trong một tam giác vuông, bình phương cạnh huyền bằng tổng bình phương hai cạnh góc vuông.</div></div></div></div><div class="question c64a92e9defb726e3b384da7e" style="border-bottom: none; box-sizing: border-box; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%; text-align: inherit;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 7 : Cho tam giác ABC vuông cân ở A. Tính độ dài BC biết AB = AC = 2 dm</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">BC = 4 dm.        </div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>B</mi><mi>C</mi><mo>=</mo><msqrt><mn>64</mn></msqrt><mi>d</mi><mi>m</mi></math>" id="MathJax-Element-14-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=√64<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.003em; padding-top: 0.477em; white-space: pre;">d<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>64</mn></msqrt><mi>�</mi><mi>�</mi></math>.       </div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">BC = 8 dm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>B</mi><mi>C</mi><mo>=</mo><msqrt><mn>8</mn></msqrt><mi>d</mi><mi>m</mi></math>" id="MathJax-Element-15-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=√8<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.003em; padding-top: 0.477em; white-space: pre;">d<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>8</mn></msqrt><mi>�</mi><mi>�</mi></math></div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : D<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Tam giác ABC  vuông cân ở A nên theo định lý Pythagore ta có <mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-16-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math>  màAB = AC = 2 dmNên <mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>2</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>2</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>8</mn><mo stretchy="false">&#x21D2;</mo><mi>B</mi><mi>C</mi><mo>=</mo><msqrt><mn>8</mn></msqrt><mi>d</mi><mi>m</mi></math>" id="MathJax-Element-17-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=22+22=8⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=√8<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.003em; padding-top: 0.477em; white-space: pre;">d<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>2</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>2</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>8</mn><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>8</mn></msqrt><mi>�</mi><mi>�</mi></math></div></div></div></div><div class="question c64a92e9defb726e3b384da84" style="border-bottom: none; box-sizing: border-box; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%; text-align: inherit;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 8 : Cho hình vẽ. Tính x.<img alt="" height="224" src="https://tailieumoi.vn/storage/uploads/images/74117/14-1703747687.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" /></div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 10 cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 11 cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 8 cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 5 cm</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : D<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Áp dụng định lí Pythagore cho tam giác ABC vuông tại B ta được :<mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>13</mn><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>12</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>25</mn><mo stretchy="false">&#x21D2;</mo><mi>x</mi><mo>=</mo><mn>5</mn><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-18-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2=132−122=25⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x=5<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>13</mn><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>12</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>25</mn><mo stretchy="false">⇒</mo><mi>�</mi><mo>=</mo><mn>5</mn><mi>�</mi><mi>�</mi></math>Vậy x = 5 cm</div></div></div></div><div class="question c64a92e9eefb726e3b384da8a" style="border-bottom: none; box-sizing: border-box; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%; text-align: inherit;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 9 : Một tam giác vuông có cạnh huyền bằng 26cm độ dài các cạnh góc vuông tỉ lệ với 5 và 12. Tính độ dài các cạnh góc vuông.</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">12cm ; 24cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">10cm ; 22 cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">10cm ; 24cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">15cm ; 24cm.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : C<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải  :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Gọi độ dài hai cạnh góc vuông là <mi>x</mi><mo>,</mo><mi>y</mi><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mi>x</mi><mo>,</mo><mi>y</mi><mo>&gt;</mo><mn>0</mn></mrow><mo>)</mo></mrow></math>" id="MathJax-Element-19-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x,<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x,<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y>0)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mo>,</mo><mi>�</mi><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mi>�</mi><mo>,</mo><mi>�</mi><mo>></mo><mn>0</mn></mrow><mo>)</mo></mrow></math>Theo định lý Pytago ta có: <mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>y</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>26</mn><msup><mrow class="MJX-TeXAtom-ORD"></mrow><mn>2</mn></msup><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>y</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>676</mn></math>" id="MathJax-Element-20-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y2=262⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y2=676<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>26</mn><msup><mrow class="MJX-TeXAtom-ORD"></mrow><mn>2</mn></msup><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>676</mn></math>Theo đề bài ta có: <mfrac><mi>x</mi><mn>5</mn></mfrac><mo>=</mo><mfrac><mi>y</mi><mrow class="MJX-TeXAtom-ORD"><mn>12</mn></mrow></mfrac><mo stretchy="false">&#x21D2;</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>25</mn></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi>y</mi><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>144</mn></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>y</mi><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>25</mn><mo>+</mo><mn>144</mn></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>676</mn></mrow><mrow class="MJX-TeXAtom-ORD"><mn>169</mn></mrow></mfrac><mo>=</mo><mn>4</mn></math>" id="MathJax-Element-21-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x5=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y12⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x225=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y2144=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y225+144=676169=4<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mi>�</mi><mn>5</mn></mfrac><mo>=</mo><mfrac><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mn>12</mn></mrow></mfrac><mo stretchy="false">⇒</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>25</mn></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>144</mn></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>25</mn><mo>+</mo><mn>144</mn></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>676</mn></mrow><mrow class="MJX-TeXAtom-ORD"><mn>169</mn></mrow></mfrac><mo>=</mo><mn>4</mn></math>Suy ra <mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>25.4</mn><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>100</mn><mo stretchy="false">&#x21D2;</mo><mi>x</mi><mo>=</mo><mn>10</mn><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-22-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2=25.4⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2=100⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x=10<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>25.4</mn><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>100</mn><mo stretchy="false">⇒</mo><mi>�</mi><mo>=</mo><mn>10</mn><mi>�</mi><mi>�</mi></math><mrow class="MJX-TeXAtom-ORD"><msup><mi>y</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>144.4</mn><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>y</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>576</mn><mo stretchy="false">&#x21D2;</mo><mi>y</mi><mo>=</mo><mn>24</mn><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-23-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y2=144.4⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y2=576⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y=24<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>144.4</mn><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>576</mn><mo stretchy="false">⇒</mo><mi>�</mi><mo>=</mo><mn>24</mn><mi>�</mi><mi>�</mi></math></div></div></div></div><div class="question c64a92e9eefb726e3b384da90" style="border-bottom: none; box-sizing: border-box; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%; text-align: inherit;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 10 : Cho hình vẽ sau. Tính <mi>x</mi></math>" id="MathJax-Element-24-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi></math>.<img alt="" height="134" src="https://tailieumoi.vn/storage/uploads/images/74117/15-1703747710.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" /></div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mn>5</mn></math>" id="MathJax-Element-25-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">5<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>5</mn></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mn>5</mn><msqrt><mn>4</mn></msqrt></math>" id="MathJax-Element-26-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">5√4<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>5</mn><msqrt><mn>4</mn></msqrt></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mn>4</mn></math>" id="MathJax-Element-27-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">4<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>4</mn></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mn>4</mn><msqrt><mn>5</mn></msqrt></math>" id="MathJax-Element-28-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">4√5<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>4</mn><msqrt><mn>5</mn></msqrt></math>.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : D<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><img alt="" height="188" src="https://tailieumoi.vn/storage/uploads/images/74117/16-1703747721.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" />Kẻ <mi>A</mi><mi>H</mi><mi mathvariant="normal">&#x22A5;</mi><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>D</mi></mrow></mrow></math>" id="MathJax-Element-29-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H⊥<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mi mathvariant="normal">⊥</mi><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow></math> tại H.Khi đó ACDH là hình chữ nhật, suy ra: HD = AC = 6; AH = CD = 8.Do đó: BH = BD – HD = 10 – 6 = 4Áp dụng định lí Pythagore cho tam giác AHB vuông tại H, ta có:<mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>80</mn><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mi>B</mi><mo>=</mo><mn>4</mn><msqrt><mn>5</mn></msqrt></math>" id="MathJax-Element-30-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=42+82=80⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B=4√5<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>80</mn><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><mn>4</mn><msqrt><mn>5</mn></msqrt></math>Vậy <mi>x</mi><mo>=</mo><mn>4</mn><msqrt><mn>5</mn></msqrt></math>" id="MathJax-Element-31-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x=4√5<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mo>=</mo><mn>4</mn><msqrt><mn>5</mn></msqrt></math></div></div></div></div>Câu 11 : Cho tam giác ABC cân tại A. Kẻ AH  vuông góc với BC tại H. Cho BH = 5cm , AB = 13cm. Tính diện tích tam giác ABC:</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mn>12</mn><mi>c</mi><msup><mi>m</mi><mn>2</mn></msup></math>" id="MathJax-Element-32-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">12<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>12</mn><mi>�</mi><msup><mi>�</mi><mn>2</mn></msup></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mn>36</mn><mi>c</mi><msup><mi>m</mi><mn>2</mn></msup></math>" id="MathJax-Element-33-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">36<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>36</mn><mi>�</mi><msup><mi>�</mi><mn>2</mn></msup></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mn>40</mn><mi>c</mi><msup><mi>m</mi><mn>2</mn></msup></math>" id="MathJax-Element-34-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">40<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>40</mn><mi>�</mi><msup><mi>�</mi><mn>2</mn></msup></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mn>60</mn><mi>c</mi><msup><mi>m</mi><mn>2</mn></msup></math>" id="MathJax-Element-35-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">60<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>60</mn><mi>�</mi><msup><mi>�</mi><mn>2</mn></msup></math>.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : D<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><img alt="" height="149" src="https://tailieumoi.vn/storage/uploads/images/74117/18-1703747770.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="225" />Xét tam giác ABC cân tại A có AH  là đường cao, suy ra AH là đường trung tuyến.<mo stretchy="false">&#x21D2;</mo><mi>B</mi><mi>C</mi><mo>=</mo><mn>2.</mn><mi>B</mi><mi>H</mi><mo>=</mo><mn>2.5</mn><mo>=</mo><mn>10</mn><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-36-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=2.<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H=2.5=10<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><mn>2.</mn><mi>�</mi><mi>�</mi><mo>=</mo><mn>2.5</mn><mo>=</mo><mn>10</mn><mi>�</mi><mi>�</mi></math>Xét tam giác ABH có AH là đường cao <mo stretchy="false">&#x21D2;</mo><mi>A</mi><mi>H</mi><mi mathvariant="normal">&#x22A5;</mi><mi>H</mi><mi>B</mi></math>" id="MathJax-Element-37-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H⊥<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mi mathvariant="normal">⊥</mi><mi>�</mi><mi>�</mi></math> nên tam giác ABH vuông tại H.Áp dụng định lí Pythagore vào tam giác vuông ABH, ta có:<mi>A</mi><mi>H</mi><mo>=</mo><msqrt><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow></msqrt><mo>=</mo><msqrt><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mn>13</mn></mrow><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>5</mn><mn>2</mn></msup></mrow></msqrt><mo>=</mo><msqrt><mn>144</mn></msqrt><mo>=</mo><mn>12</mn><mo stretchy="false">(</mo><mi>c</mi><mi>m</mi><mo stretchy="false">)</mo></math>" id="MathJax-Element-38-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H=√<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=√132−52=√144=12(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></msqrt><mo>=</mo><msqrt><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mn>13</mn></mrow><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>5</mn><mn>2</mn></msup></mrow></msqrt><mo>=</mo><msqrt><mn>144</mn></msqrt><mo>=</mo><mn>12</mn><mo stretchy="false">(</mo><mi>�</mi><mi>�</mi><mo stretchy="false">)</mo></math>Vậy diện tích tam giác ABC là: <mfrac><mn>1</mn><mn>2</mn></mfrac><mi>A</mi><mi>H</mi><mo>.</mo><mi>B</mi><mi>C</mi><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mn>.12</mn><mn>.10</mn><mo>=</mo><mn>60</mn><mo stretchy="false">(</mo><mi>c</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>m</mi><mn>2</mn></msup></mrow><mo stretchy="false">)</mo></math>" id="MathJax-Element-39-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">12<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H.<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=12.12.10=60(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m2)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>�</mi><mi>�</mi><mo>.</mo><mi>�</mi><mi>�</mi><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mn>.12</mn><mn>.10</mn><mo>=</mo><mn>60</mn><mo stretchy="false">(</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">)</mo></math></div></div></div></div><div class="question c64a930ebefb726e3b384dae4" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 12 : Tam giác nào là tam giác vuông trong các tam giác có độ dài ba cạnh như sau:</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">15cm; 8cm; 18cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">21dm; 20dm; 29dm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">5m; 6m; 8m.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">2m; 3m; 4m.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : B<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải:</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">+) Với bộ số: 15cm; 8cm; 18cm  ta thấy : <mrow class="MJX-TeXAtom-ORD"><msup><mn>18</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>324</mn><mrow class="MJX-TeXAtom-ORD"><msup><mo>,</mo><mrow class="MJX-TeXAtom-ORD"></mrow></msup></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mn>15</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>289</mn><mo>&lt;</mo><mn>324</mn></math>" id="MathJax-Element-40-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">182=324,152+82=289<324<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><msup><mn>18</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>324</mn><mrow class="MJX-TeXAtom-ORD"><msup><mo>,</mo><mrow class="MJX-TeXAtom-ORD"></mrow></msup></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mn>15</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>289</mn><mo><</mo><mn>324</mn></math> nên loại đáp án A.+) Với bộ số: 21dm; 20dm; 29dm  ta thấy : <mrow class="MJX-TeXAtom-ORD"><msup><mn>29</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>841</mn><mrow class="MJX-TeXAtom-ORD"><msup><mo>;</mo><mrow class="MJX-TeXAtom-ORD"></mrow></msup></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mn>21</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>20</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>841</mn><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>29</mn><mn>2</mn></msup></mrow></math>" id="MathJax-Element-41-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">292=841;212+202=841=292<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><msup><mn>29</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>841</mn><mrow class="MJX-TeXAtom-ORD"><msup><mo>;</mo><mrow class="MJX-TeXAtom-ORD"></mrow></msup></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mn>21</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>20</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>841</mn><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>29</mn><mn>2</mn></msup></mrow></math> nên đây là ba cạnh của tam giác vuông.+) Với bộ số: 5m; 6m; 8m ta thấy : <mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>64</mn><mrow class="MJX-TeXAtom-ORD"><msup><mo>;</mo><mrow class="MJX-TeXAtom-ORD"></mrow></msup></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mn>5</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>6</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>61</mn><mo>&lt;</mo><mn>64</mn></math>" id="MathJax-Element-42-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">82=64;52+62=61<64<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>64</mn><mrow class="MJX-TeXAtom-ORD"><msup><mo>;</mo><mrow class="MJX-TeXAtom-ORD"></mrow></msup></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mn>5</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>6</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>61</mn><mo><</mo><mn>64</mn></math> nên loại đáp án C.+) Với bộ số: 2m; 3m; 4m ta thấy : <mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>16</mn><mrow class="MJX-TeXAtom-ORD"><msup><mo>;</mo><mrow class="MJX-TeXAtom-ORD"></mrow></msup></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mn>3</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>2</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>13</mn><mo>&lt;</mo><mn>16</mn></math>" id="MathJax-Element-43-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">42=16;32+22=13<16<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>16</mn><mrow class="MJX-TeXAtom-ORD"><msup><mo>;</mo><mrow class="MJX-TeXAtom-ORD"></mrow></msup></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mn>3</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>2</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>13</mn><mo><</mo><mn>16</mn></math> nên loại đáp án D.</div></div></div></div><div class="question c64ab5d84efb726e3b384daea" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 13 : Cho ABCD là hình vuông cạnh 4 cm (hình vẽ). Khi đó độ dài đường chéo AC là:<img alt="" height="163" src="https://tailieumoi.vn/storage/uploads/images/74117/19-1703747786.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="184" /></div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>A</mi><mi>C</mi><mo>=</mo><mn>4</mn><msqrt><mn>2</mn></msqrt><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-44-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=4√2<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><mn>4</mn><msqrt><mn>2</mn></msqrt><mi>�</mi><mi>�</mi></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>A</mi><mi>C</mi><mo>=</mo><mn>4</mn><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-45-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=4<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><mn>4</mn><mi>�</mi><mi>�</mi></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>A</mi><mi>C</mi><mo>=</mo><msqrt><mn>30</mn></msqrt><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-46-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=√30<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>30</mn></msqrt><mi>�</mi><mi>�</mi></math>.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>A</mi><mi>C</mi><mo>=</mo><mn>8</mn><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-47-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=8<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><mn>8</mn><mi>�</mi><mi>�</mi></math>.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : A<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải:</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Vì ABCD là hình vuông nên AB = AC = 4cmÁp dụng định lý Pythagore: Trong một tam giác vuông, bình phương hai cạnh huyền bằng tổng bình phương hai cạnh góc vuông. cho tam giác ABC vuông tại B ta có<mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>32</mn><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mi>C</mi><mo>=</mo><msqrt><mn>32</mn></msqrt><mo>=</mo><mn>4</mn><msqrt><mn>2</mn></msqrt><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-48-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=42+42=32⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=√32=4√2<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>32</mn><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>32</mn></msqrt><mo>=</mo><mn>4</mn><msqrt><mn>2</mn></msqrt><mi>�</mi><mi>�</mi></math></div></div></div></div><div class="question c64ab5d86efb726e3b384daf0" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 14 : Tìm câu sai trong các câu sau đây. Cho tam giác PQR vuông tại P. Khi đó:</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">QR > PQ</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">QR > PR</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>Q</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>R</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>P</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>Q</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>P</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>R</mi></mrow></mrow><mn>2</mn></msup></mrow></math>" id="MathJax-Element-49-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-top: 0.477em; white-space: pre;">Q<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">R2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.109em; padding-top: 0.477em; white-space: pre;">P<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-top: 0.477em; white-space: pre;">Q2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.109em; padding-top: 0.477em; white-space: pre;">P<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">R2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow></math></div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mi>Q</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>R</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>+</mo><mi>P</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>R</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>P</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>Q</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-50-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-top: 0.477em; white-space: pre;">Q<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">R2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.109em; padding-top: 0.477em; white-space: pre;">P<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">R2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.109em; padding-top: 0.477em; white-space: pre;">P<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-top: 0.477em; white-space: pre;">Q2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math></div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : D<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><img alt="" height="231" src="https://tailieumoi.vn/storage/uploads/images/74117/20-1703747802.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="221" />Tam giác PQR vuông tại P nên theo định lí Pythagore ta có: <mi>Q</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>R</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>P</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>Q</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>P</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>R</mi></mrow></mrow><mn>2</mn></msup></mrow></math>" id="MathJax-Element-51-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-top: 0.477em; white-space: pre;">Q<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">R2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.109em; padding-top: 0.477em; white-space: pre;">P<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-top: 0.477em; white-space: pre;">Q2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.109em; padding-top: 0.477em; white-space: pre;">P<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">R2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow></math> nên câu C đúng.Vì độ dài đoạn thẳng là một số dương nên QR > PQ; QR > PRSuy ra các câu A, B đúng.Câu trả lời sai là câu D.</div></div></div></div><div class="question c64ab5d88efb726e3b384dafa" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 15 : Cho tam giác ABC vuông ở A có AC = 20 cm. Kẻ <mi>A</mi><mi>H</mi><mi mathvariant="normal">&#x22A5;</mi><mi>B</mi><mi>C</mi></math>" id="MathJax-Element-52-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H⊥<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mi mathvariant="normal">⊥</mi><mi>�</mi><mi>�</mi></math>. Biết BH = 9cm; HC = 16cm. Tính AB , AH</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">AH = 12cm; AB = 15cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">AH = 10cm; AB = 15 cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">AH = 15cm; AB = 12cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">AH = 12cm; AB = 13 cm.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : A<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><img alt="" height="214" src="https://tailieumoi.vn/storage/uploads/images/74117/21-1703747816.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="359" />+) Ta có: BC = BH + HC = 9 + 16 = 25 cm+) Xét tam giác ABC vuông tại A, theo định lí Pythagore ta có:<mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>25</mn><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>20</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>225</mn><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mi>B</mi><mo>=</mo><mn>15</mn><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-53-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=252−202=225⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B=15<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>25</mn><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>20</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>225</mn><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><mn>15</mn><mi>�</mi><mi>�</mi></math>+) Xét tam giác ABH vuông tại H, theo định lí Pythagore ta có:<mi>H</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>H</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>A</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>H</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>15</mn><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>9</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>144</mn><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mi>H</mi><mo>=</mo><mn>12</mn><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-54-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=152−92=144⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H=12<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>15</mn><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>9</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>144</mn><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><mn>12</mn><mi>�</mi><mi>�</mi></math>+) Vậy AH = 12cm ; AB = 15cm</div></div></div></div><div class="question c64ab5d88efb726e3b384db00" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 16 : Cho tam giác ABC. Kẻ AH vuông góc với BC. Tính chu vi tam giác ABC biết AB = 5cm, AH = 4 cm, <mi>H</mi><mi>C</mi><mo>=</mo><msqrt><mn>184</mn></msqrt><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-55-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=√184<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>184</mn></msqrt><mi>�</mi><mi>�</mi></math>. (làm tròn đến chữ số thập phân thứ nhất).</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">30,8cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">35, 7cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">31 cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">31, 7cm.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : B<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><img alt="" height="159" src="https://tailieumoi.vn/storage/uploads/images/74117/2-1703747836.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="260" />Áp dụng định lí Pythagore cho tam giác ABH vuông tại H, ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>5</mn><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>9</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>B</mi><mi>H</mi><mo>=</mo><mn>3</mn><mo stretchy="false">(</mo><mi>c</mi><mi>m</mi><mo stretchy="false">)</mo></mtd></mtr></mtable></math>" id="MathJax-Element-56-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=52−42=9⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H=3(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>5</mn><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>9</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><mn>3</mn><mo stretchy="false">(</mo><mi>�</mi><mi>�</mi><mo stretchy="false">)</mo></mtd></mtr></mtable></math>Suy ra: <mi>B</mi><mi>C</mi><mo>=</mo><mi>H</mi><mi>B</mi><mo>+</mo><mi>H</mi><mi>C</mi><mo>=</mo><mn>3</mn><mo>+</mo><msqrt><mn>184</mn></msqrt></math>" id="MathJax-Element-57-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=3+√184<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><mi>�</mi><mi>�</mi><mo>+</mo><mi>�</mi><mi>�</mi><mo>=</mo><mn>3</mn><mo>+</mo><msqrt><mn>184</mn></msqrt></math>Áp dụng định lí Pythagore cho tam giác AHC vuông tại H ta có:<mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>C</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><msqrt><mn>184</mn></msqrt></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>200</mn><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mi>C</mi><mo>=</mo><msqrt><mn>200</mn></msqrt></math>" id="MathJax-Element-58-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=42+(√184)2=200⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=√200<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>4</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><msqrt><mn>184</mn></msqrt></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>200</mn><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>200</mn></msqrt></math>Vậy chu vi tam giác ABC là: <mi>A</mi><mi>B</mi><mo>+</mo><mi>A</mi><mi>C</mi><mo>+</mo><mi>B</mi><mi>C</mi><mo>=</mo><mn>5</mn><mo>+</mo><msqrt><mn>200</mn></msqrt><mo>+</mo><mn>3</mn><mo>+</mo><msqrt><mn>184</mn></msqrt><mo>&#x2248;</mo><mn>35</mn><mo>,</mo><mn>7</mn><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-59-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=5+√200+3+√184≈35,7<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>+</mo><mi>�</mi><mi>�</mi><mo>+</mo><mi>�</mi><mi>�</mi><mo>=</mo><mn>5</mn><mo>+</mo><msqrt><mn>200</mn></msqrt><mo>+</mo><mn>3</mn><mo>+</mo><msqrt><mn>184</mn></msqrt><mo>≈</mo><mn>35</mn><mo>,</mo><mn>7</mn><mi>�</mi><mi>�</mi></math></div></div></div></div><div class="question c64ab5d88efb726e3b384db0a" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 17 : Tính cạnh huyền của một tam giác vuông biết tỉ số các cạnh góc vuông là 3 : 4 và chu vi tam giác là 36 cm</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">9cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">12cm .  </div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">15cm.</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">16cm.</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : C<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Gọi độ dài hai cạnh góc vuông là <mi>x</mi><mo>,</mo><mi>y</mi><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mi>y</mi><mo>&gt;</mo><mi>x</mi><mo>&gt;</mo><mn>0</mn></mrow><mo>)</mo></mrow></math>" id="MathJax-Element-60-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x,<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x>0)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mo>,</mo><mi>�</mi><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mi>�</mi><mo>></mo><mi>�</mi><mo>></mo><mn>0</mn></mrow><mo>)</mo></mrow></math> (cm) và độ dài cạnh huyền là <mi>z</mi><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mi>z</mi><mo>&gt;</mo><mi>y</mi></mrow><mo>)</mo></mrow></math>" id="MathJax-Element-61-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.003em; padding-top: 0.24em; white-space: pre;">z(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.003em; padding-top: 0.24em; white-space: pre;">z><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mi>�</mi><mo>></mo><mi>�</mi></mrow><mo>)</mo></mrow></math>(cm)Theo đề bài ta có <mfrac><mi>x</mi><mn>3</mn></mfrac><mo>=</mo><mfrac><mi>y</mi><mn>4</mn></mfrac></math>" id="MathJax-Element-62-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x3=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y4<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mi>�</mi><mn>3</mn></mfrac><mo>=</mo><mfrac><mi>�</mi><mn>4</mn></mfrac></math> và x + y + z = 36Đặt <mfrac><mi>x</mi><mn>3</mn></mfrac><mo>=</mo><mfrac><mi>y</mi><mn>4</mn></mfrac><mo>=</mo><mi>k</mi><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mi>k</mi><mo>&gt;</mo><mn>0</mn></mrow><mo>)</mo></mrow><mo stretchy="false">&#x21D2;</mo><mi>x</mi><mo>=</mo><mn>3</mn><mi>k</mi><mo>;</mo><mi>y</mi><mo>=</mo><mn>4</mn><mi>k</mi></math>" id="MathJax-Element-63-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x3=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y4=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k>0)⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x=3<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k;<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y=4<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mi>�</mi><mn>3</mn></mfrac><mo>=</mo><mfrac><mi>�</mi><mn>4</mn></mfrac><mo>=</mo><mi>�</mi><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mi>�</mi><mo>></mo><mn>0</mn></mrow><mo>)</mo></mrow><mo stretchy="false">⇒</mo><mi>�</mi><mo>=</mo><mn>3</mn><mi>�</mi><mo>;</mo><mi>�</mi><mo>=</mo><mn>4</mn><mi>�</mi></math>Theo định lý Pythagore ta có: <mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>y</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>z</mi><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>z</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>3</mn><mi>k</mi></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>4</mn><mi>k</mi></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>25</mn><mrow class="MJX-TeXAtom-ORD"><msup><mi>k</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>5</mn><mi>k</mi></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mi>z</mi><mo>=</mo><mn>5</mn><mi>k</mi></math>" id="MathJax-Element-64-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.003em; padding-top: 0.24em; white-space: pre;">z2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.003em; padding-top: 0.24em; white-space: pre;">z2=(3<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k)2+(4<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k)2=25<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k2=(5<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k)2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.003em; padding-top: 0.24em; white-space: pre;">z=5<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>3</mn><mi>�</mi></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>4</mn><mi>�</mi></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>25</mn><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>5</mn><mi>�</mi></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mi>�</mi><mo>=</mo><mn>5</mn><mi>�</mi></math>Suy ra <mi>x</mi><mo>+</mo><mi>y</mi><mo>+</mo><mi>z</mi><mo>=</mo><mn>3</mn><mi>k</mi><mo>+</mo><mn>4</mn><mi>k</mi><mo>+</mo><mn>5</mn><mi>k</mi><mo>=</mo><mn>12</mn><mi>k</mi><mo>=</mo><mn>36</mn><mo stretchy="false">&#x21D2;</mo><mi>k</mi><mo>=</mo><mn>3</mn></math>" id="MathJax-Element-65-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.003em; padding-top: 0.24em; white-space: pre;">z=3<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k+4<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k+5<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k=12<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k=36⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">k=3<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mo>+</mo><mi>�</mi><mo>+</mo><mi>�</mi><mo>=</mo><mn>3</mn><mi>�</mi><mo>+</mo><mn>4</mn><mi>�</mi><mo>+</mo><mn>5</mn><mi>�</mi><mo>=</mo><mn>12</mn><mi>�</mi><mo>=</mo><mn>36</mn><mo stretchy="false">⇒</mo><mi>�</mi><mo>=</mo><mn>3</mn></math> (thỏa mãn)Từ đó: <mi>x</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mn>9</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mi>c</mi><mi>m</mi><mo>;</mo><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mi>y</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mn>12</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mi>c</mi><mi>m</mi><mo>;</mo><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mi>z</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mn>15</mn><mi>c</mi><mi>m</mi><mo>.</mo></math>" id="MathJax-Element-66-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x=9<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m;<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.477em; padding-right: 0.006em; padding-top: 0.24em; white-space: pre;">y=12<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m;<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.003em; padding-top: 0.24em; white-space: pre;">z=15<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m.<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mn>9</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mi>�</mi><mi>�</mi><mo>;</mo><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mn>12</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mi>�</mi><mi>�</mi><mo>;</mo><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"></mrow></mrow><mn>15</mn><mi>�</mi><mi>�</mi><mo>.</mo></math>Vậy cạnh huyền dài 15 cm</div></div></div></div><div class="question c64ab5d89efb726e3b384db10" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 18 : Tìm x trong hình vẽ sau:<img alt="" height="226" src="https://tailieumoi.vn/storage/uploads/images/74117/22-1703747850.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="197" /></div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 6</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 7</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 8</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 5</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : B<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Áp dụng định lý Pythagore: Trong một tam giác vuông, bình phương hai cạnh huyền bằng tổng bình phương hai cạnh góc vuông. vào Tam giác ABH vuông tại H ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>9</mn><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>3</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>72</mn></mtd></mtr></mtable></math>" id="MathJax-Element-67-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=92−32=72<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>9</mn><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>3</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>72</mn></mtd></mtr></mtable></math>Áp dụng định lý Pythagore: Trong một tam giác vuông, bình phương hai cạnh huyền bằng tổng bình phương hai cạnh góc vuông. vào tam giác ACH vuông tại H ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>H</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>H</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>11</mn><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mn>72</mn><mo>=</mo><mn>49</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>x</mi><mo>=</mo><mi>H</mi><mi>C</mi><mo>=</mo><msqrt><mn>49</mn></msqrt><mo>=</mo><mn>7</mn></mtd></mtr></mtable></math>" id="MathJax-Element-68-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=112−72=49⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=√49=7<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>11</mn><mn>2</mn></msup></mrow><mo>−</mo><mn>72</mn><mo>=</mo><mn>49</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mo>=</mo><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>49</mn></msqrt><mo>=</mo><mn>7</mn></mtd></mtr></mtable></math></div></div></div></div><div class="question c64ab5d89efb726e3b384db16" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 19 : Tìm x trong hình vẽ sau:<img alt="" height="178" src="https://tailieumoi.vn/storage/uploads/images/74117/23-1703747867.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="231" /></div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 2</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 1,5</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 1</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">x = 1,2</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : C<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Tam giác ABC vuông tại A nên <mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>A</mi><mi>B</mi><mi>C</mi></mrow><mo>^</mo></mover></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>A</mi><mi>C</mi><mi>B</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>o</mi></msup></mrow><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>A</mi><mi>B</mi><mi>C</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>o</mi></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>A</mi><mi>C</mi><mi>B</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>o</mi></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>30</mn><mi>o</mi></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>60</mn><mi>o</mi></msup></mrow></math>" id="MathJax-Element-69-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C+ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B=90<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o⇒ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=90<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o−ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B=90<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o−30<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o=60<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mi>�</mi></mrow><mo>^</mo></mover></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mi>�</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>�</mi></msup></mrow><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mi>�</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>�</mi></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mi>�</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>�</mi></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>30</mn><mi>�</mi></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>60</mn><mi>�</mi></msup></mrow></math>.Lại có BD là tia phân giác của <mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>A</mi><mi>B</mi><mi>C</mi></mrow><mo>^</mo></mover></mrow></math>" id="MathJax-Element-70-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mi>�</mi></mrow><mo>^</mo></mover></mrow></math> (gỉa thiết) nên : <mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>A</mi><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>D</mi></mrow></mrow></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>D</mi><mi>B</mi><mi>C</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>A</mi><mi>B</mi><mi>C</mi></mrow><mo>^</mo></mover></mrow></mrow><mn>2</mn></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mn>60</mn></mrow><mi>o</mi></msup></mrow></mrow><mn>2</mn></mfrac><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>30</mn><mi>o</mi></msup></mrow></math>" id="MathJax-Element-71-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D=ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=60<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o2=30<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mi>�</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mi>�</mi></mrow><mo>^</mo></mover></mrow></mrow><mn>2</mn></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mn>60</mn></mrow><mi>�</mi></msup></mrow></mrow><mn>2</mn></mfrac><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>30</mn><mi>�</mi></msup></mrow></math>.Tam giác ABC vuông tại A có <mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>A</mi><mi>C</mi><mi>B</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>30</mn><mi>o</mi></msup></mrow></math>" id="MathJax-Element-72-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B=30<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mi>�</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>30</mn><mi>�</mi></msup></mrow></math> nên <mi>A</mi><mi>B</mi><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>B</mi><mi>C</mi></math>" id="MathJax-Element-73-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B=12<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>�</mi><mi>�</mi></math> hay BC = 2 AB.Áp dụng định lý Pythagore vào tam giác ABC vuông tại A ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>A</mi></mrow></mrow><mi>B</mi></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>3</mn><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mn>4</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>A</mi></mrow></mrow><mi>B</mi><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mn>9</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mn>3</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>A</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>9</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>3</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mi>B</mi><mo>=</mo><msqrt><mn>3</mn></msqrt></mtd></mtr></mtable></math>" id="MathJax-Element-74-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2⇒(2<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B)2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+32⇒4<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+9⇒3<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=9⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=3⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B=√3<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mi>�</mi></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>3</mn><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mn>4</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mi>�</mi><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mn>9</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mn>3</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>9</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>3</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><msqrt><mn>3</mn></msqrt></mtd></mtr></mtable></math>Tam giác ABC vuông tại A có: <mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>A</mi><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>D</mi></mrow></mrow></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>30</mn><mi>o</mi></msup></mrow></math>" id="MathJax-Element-75-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D=30<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>30</mn><mi>�</mi></msup></mrow></math> nên <mi>A</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>D</mi></mrow></mrow><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>D</mi></mrow></mrow></math>" id="MathJax-Element-76-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D=12<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow></math> hay BD = 2AD.Áp dụng định lý Pythagore vào tam giác ABD vuông tại A ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>D</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>D</mi></mrow></mrow><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>A</mi><mi>D</mi></mrow></mrow></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>D</mi></mrow></mrow><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mi>x</mi></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><msqrt><mn>3</mn></msqrt></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mn>4</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>x</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>3</mn><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mn>3</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>x</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>3</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>1</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>x</mi><mo>=</mo><mn>1</mn></mtd></mtr></mtable></math>" id="MathJax-Element-77-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D2⇒(2<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D)2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D2⇒(2<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x)2=(√3)2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2⇒4<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2=3+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2⇒3<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2=3⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2=1⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x=1<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi><mi>�</mi></mrow></mrow></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mi>�</mi></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><msqrt><mn>3</mn></msqrt></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mn>4</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>3</mn><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mn>3</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>3</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>1</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mo>=</mo><mn>1</mn></mtd></mtr></mtable></math></div></div></div></div><div class="question c64ab5d8aefb726e3b384db1c" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 20 : Tìm câu trả lời sai. Cho hình vẽ biết DE // HK. Khi đó:<img alt="" height="157" src="https://tailieumoi.vn/storage/uploads/images/74117/24-1703747880.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="304" /></div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">DK = 9</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>E</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>D</mi></mrow></mrow><mi>H</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>o</mi></msup></mrow></math>" id="MathJax-Element-78-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.026em; padding-top: 0.477em; white-space: pre;">E<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H=90<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mi>�</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>�</mi></msup></mrow></math></div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">DK = 10</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>D</mi><mi>H</mi><mi>K</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>o</mi></msup></mrow></math>" id="MathJax-Element-79-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.04em; padding-top: 0.477em; white-space: pre;">K=90<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mi>�</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>�</mi></msup></mrow></math></div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : C<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải  :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Ta có DE // HK nên: <mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>E</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>D</mi></mrow></mrow><mi>H</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>D</mi><mi>H</mi><mi>K</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>o</mi></msup></mrow></math>" id="MathJax-Element-80-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.026em; padding-top: 0.477em; white-space: pre;">E<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H=ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.04em; padding-top: 0.477em; white-space: pre;">K=90<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">o<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi>�</mi></mrow></mrow><mi>�</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><mover><mrow><mi>�</mi><mi>�</mi><mi>�</mi></mrow><mo>^</mo></mover></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>90</mn><mi>�</mi></msup></mrow></math> (so le trong)Áp dụng định lí Pythagore trong tam giác vuông DHK ta được:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>D</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>K</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>D</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>H</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>K</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>D</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>K</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><msqrt><mn>17</mn></msqrt></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>D</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>K</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>64</mn><mo>+</mo><mn>17</mn><mo>=</mo><mn>81</mn><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>9</mn><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mi>D</mi><mi>K</mi><mo>=</mo><mn>9</mn></mtd></mtr></mtable></math>" id="MathJax-Element-81-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.04em; padding-top: 0.477em; white-space: pre;">K2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.04em; padding-top: 0.477em; white-space: pre;">K2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.04em; padding-top: 0.477em; white-space: pre;">K2=82+(√17)2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.04em; padding-top: 0.477em; white-space: pre;">K2=64+17=81=92<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">D<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.04em; padding-top: 0.477em; white-space: pre;">K=9<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><msqrt><mn>17</mn></msqrt></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>64</mn><mo>+</mo><mn>17</mn><mo>=</mo><mn>81</mn><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>9</mn><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mi>�</mi><mi>�</mi><mo>=</mo><mn>9</mn></mtd></mtr></mtable></math></div></div></div></div><div class="question c64ab750befb726e3b384db91" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 21 : Cho tam giác ABC biết BC = 7,5cm; CA = 4,5cm, AB = 6cm. Độ dài đường cao AH của tam giác ABC là:</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">12,96cm</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">6,48cm</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">3,6cm</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">6,3cm</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : C<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải  :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><img alt="" height="210" src="https://tailieumoi.vn/storage/uploads/images/74117/25-1703747903.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="317" /><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>7</mn><mo>,</mo><mn>5</mn></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>56</mn><mo>,</mo><mn>25</mn></math>" id="MathJax-Element-82-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=(7,5)2=56,25<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>7</mn><mo>,</mo><mn>5</mn></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>56</mn><mo>,</mo><mn>25</mn></math><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>4</mn><mo>,</mo><mn>5</mn></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>6</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>56</mn><mo>,</mo><mn>25</mn></math>" id="MathJax-Element-83-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=(4,5)2+62=56,25<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mn>4</mn><mo>,</mo><mn>5</mn></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>6</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>56</mn><mo>,</mo><mn>25</mn></math>Ta thấy: <mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-84-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math>Suy ra tam giác ABC vuông tại A.Ta lại có: <mi>A</mi><mi>B</mi><mo>.</mo><mi>A</mi><mi>C</mi><mo>=</mo><mi>A</mi><mi>H</mi><mo>.</mo><mi>B</mi><mi>C</mi><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mi>H</mi><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mi>A</mi><mi>B</mi><mo>.</mo><mi>A</mi><mi>C</mi></mrow><mrow class="MJX-TeXAtom-ORD"><mi>B</mi><mi>C</mi></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>6.4</mn><mo>,</mo><mn>5</mn></mrow><mrow class="MJX-TeXAtom-ORD"><mn>7</mn><mo>,</mo><mn>5</mn></mrow></mfrac><mo>=</mo><mn>3</mn><mo>,</mo><mn>6</mn><mo stretchy="false">(</mo><mi>c</mi><mi>m</mi><mo stretchy="false">)</mo></math>" id="MathJax-Element-85-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B.<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H.<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B.<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=6.4,57,5=3,6(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>.</mo><mi>�</mi><mi>�</mi><mo>=</mo><mi>�</mi><mi>�</mi><mo>.</mo><mi>�</mi><mi>�</mi><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mi>�</mi><mi>�</mi><mo>.</mo><mi>�</mi><mi>�</mi></mrow><mrow class="MJX-TeXAtom-ORD"><mi>�</mi><mi>�</mi></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>6.4</mn><mo>,</mo><mn>5</mn></mrow><mrow class="MJX-TeXAtom-ORD"><mn>7</mn><mo>,</mo><mn>5</mn></mrow></mfrac><mo>=</mo><mn>3</mn><mo>,</mo><mn>6</mn><mo stretchy="false">(</mo><mi>�</mi><mi>�</mi><mo stretchy="false">)</mo></math></div></div></div></div><div class="question c64ab750befb726e3b384db97" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 22 : Cho tam giác ABC cân tại A biết AB = AC = 17cm. Kẻ <mi>B</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mi mathvariant="normal">&#x22A5;</mi><mi>A</mi><mi>C</mi></math>" id="MathJax-Element-86-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">BD⊥<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mi mathvariant="normal">⊥</mi><mi>�</mi><mi>�</mi></math>, biết BD = 15cm. Tính cạnh đáy BC.</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">17 cm</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">16 cm</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mn>3</mn><msqrt><mn>14</mn></msqrt></math>" id="MathJax-Element-87-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">3√14<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>3</mn><msqrt><mn>14</mn></msqrt></math>cm</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;"><mn>3</mn><msqrt><mn>34</mn></msqrt><mi>c</mi><mi>m</mi></math>" id="MathJax-Element-88-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">3√34<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; height: 1px; left: 0px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>3</mn><msqrt><mn>34</mn></msqrt><mi>�</mi><mi>�</mi></math></div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : D<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải:</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><img alt="" height="190" src="https://tailieumoi.vn/storage/uploads/images/74117/26-1703747919.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="205" />Tam giác ABD vuông tại D nên theo định lí Pythagore ta có: <mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>17</mn><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>15</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>64</mn><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mo>=</mo><mn>8</mn><mo stretchy="false">(</mo><mi>c</mi><mi>m</mi><mo stretchy="false">)</mo></math>" id="MathJax-Element-89-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">AD2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">BD2=172−152=64=82⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">AD=8(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>17</mn><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>15</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>64</mn><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mo>=</mo><mn>8</mn><mo stretchy="false">(</mo><mi>�</mi><mi>�</mi><mo stretchy="false">)</mo></math><mo stretchy="false">&#x21D2;</mo><mi>C</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mo>=</mo><mi>A</mi><mi>C</mi><mo>&#x2212;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mo>=</mo><mn>17</mn><mo>&#x2212;</mo><mn>8</mn><mo>=</mo><mn>9</mn><mo stretchy="false">(</mo><mi>c</mi><mi>m</mi><mo stretchy="false">)</mo></math>" id="MathJax-Element-90-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">CD=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">AD=17−8=9(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mo>=</mo><mi>�</mi><mi>�</mi><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mo>=</mo><mn>17</mn><mo>−</mo><mn>8</mn><mo>=</mo><mn>9</mn><mo stretchy="false">(</mo><mi>�</mi><mi>�</mi><mo stretchy="false">)</mo></math>Tam giác BCD vuông tại D nên theo định lí Pythagore ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>C</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>9</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>15</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>81</mn><mo>+</mo><mn>225</mn><mo>=</mo><mn>306</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>B</mi><mi>C</mi><mo>=</mo><mn>3</mn><msqrt><mn>34</mn></msqrt><mo stretchy="false">(</mo><mi>c</mi><mi>m</mi><mo stretchy="false">)</mo></mtd></mtr></mtable></math>" id="MathJax-Element-91-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">CD2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">BD2=92+152=81+225=306⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=3√34(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">m)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">D</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>9</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>15</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>81</mn><mo>+</mo><mn>225</mn><mo>=</mo><mn>306</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><mn>3</mn><msqrt><mn>34</mn></msqrt><mo stretchy="false">(</mo><mi>�</mi><mi>�</mi><mo stretchy="false">)</mo></mtd></mtr></mtable></math></div></div></div></div><div class="question c64ab750befb726e3b384db9d" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 23 : Tính x trong hình sau:<img alt="" height="158" src="https://tailieumoi.vn/storage/uploads/images/74117/27-1703747929.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="258" /></div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">36           </div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">40</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">42</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">30</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : B<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Áp dụng định lý Pythagore vào tam giác AHB vuông tại H ta có:<mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math>" id="MathJax-Element-92-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2(1)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math>Áp dụng định lý Pythagore vào tam giác AHC vuông tại H ta có:<mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>C</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>C</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mo stretchy="false">(</mo><mn>2</mn><mo stretchy="false">)</mo></math>" id="MathJax-Element-93-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=(2)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mo stretchy="false">(</mo><mn>2</mn><mo stretchy="false">)</mo></math>Từ (1) và (2) ta có: <mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mi>C</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-94-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2−<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>18</mn><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>32</mn><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>32</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>18</mn><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mn>1024</mn><mo>+</mo><mn>324</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mn>100</mn></mtd></mtr></mtable></math>" id="MathJax-Element-95-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2−182=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2−322⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2−322+182⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2−1024+324⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2−100<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>18</mn><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>32</mn><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>32</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>18</mn><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mn>1024</mn><mo>+</mo><mn>324</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mn>100</mn></mtd></mtr></mtable></math>Ta có: BC = BH + CH = 18 + 32 = 50Áp dụng định lý Pythagore vào tam giác ABC vuông tại A ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>50</mn><mn>2</mn></msup></mrow><mo stretchy="false">(</mo><mn>3</mn><mo stretchy="false">)</mo></mtd></mtr></mtable></math>" id="MathJax-Element-96-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2=502(3)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>50</mn><mn>2</mn></msup></mrow><mo stretchy="false">(</mo><mn>3</mn><mo stretchy="false">)</mo></mtd></mtr></mtable></math>Thay <mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mn>100</mn></math>" id="MathJax-Element-97-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2−100<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mn>100</mn></math> vào (3) ta được:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>&#x2212;</mo><mn>700</mn><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">x</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>50</mn><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">x</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>2500</mn><mo>+</mo><mn>700</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">x</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>3200</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>x</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>3200</mn><mo>:</mo><mn>2</mn><mo>=</mo><mn>1600</mn></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>x</mi><mo>=</mo><msqrt><mn>1600</mn></msqrt><mo>=</mo><mn>40</mn></mtd></mtr></mtable></math>" id="MathJax-Element-98-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2−700+x2=502⇒2x2=2500+700⇒2x2=3200⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x2=3200:2=1600⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">x=√1600=40<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>−</mo><mn>700</mn><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">x</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>50</mn><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">x</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>2500</mn><mo>+</mo><mn>700</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">x</mi></mrow></mrow><mn>2</mn></msup></mrow><mo>=</mo><mn>3200</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mn>3200</mn><mo>:</mo><mn>2</mn><mo>=</mo><mn>1600</mn></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mo>=</mo><msqrt><mn>1600</mn></msqrt><mo>=</mo><mn>40</mn></mtd></mtr></mtable></math></div></div></div></div><div class="question c64ab750cefb726e3b384dba3" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 24 : Cho tam giác ABC  có <mrow class="MJX-TeXAtom-ORD"><mover><mi>B</mi><mo>^</mo></mover></mrow><mo>,</mo><mrow class="MJX-TeXAtom-ORD"><mover><mi>C</mi><mo>^</mo></mover></mrow></math>" id="MathJax-Element-99-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B,ˆ<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><mover><mi>�</mi><mo>^</mo></mover></mrow><mo>,</mo><mrow class="MJX-TeXAtom-ORD"><mover><mi>�</mi><mo>^</mo></mover></mrow></math> là các góc nhọn. Gọi H là chân đường vuông góc hạ từ A xuống BC. Biết AH = 6cm ; BH = 4,5cm và HC = 8cm. Khi đó tam giác ABC là tam giác gì?</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác cân</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác vuông</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác vuông cân</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác đều</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : B<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><img alt="" height="162" src="https://tailieumoi.vn/storage/uploads/images/74117/28-1703747950.jpg" style="border-style: none; box-sizing: border-box; height: auto; max-width: 100%; vertical-align: middle;" width="266" />Áp dụng định lý Pythagore vào tam giác AHB vuông tại H ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mi>B</mi><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>6</mn><mn>2</mn></msup></mrow><mo>+</mo><mn>4</mn><mo>,</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>5</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>36</mn><mo>+</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>81</mn></mrow><mn>4</mn></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>225</mn></mrow><mn>4</mn></mfrac></mtd></mtr></mtable></math>" id="MathJax-Element-100-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B=62+4,52=36+814=2254<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mi>�</mi><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>6</mn><mn>2</mn></msup></mrow><mo>+</mo><mn>4</mn><mo>,</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>5</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>36</mn><mo>+</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>81</mn></mrow><mn>4</mn></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>225</mn></mrow><mn>4</mn></mfrac></mtd></mtr></mtable></math>Áp dụng định lý Pythagore vào tam giác AHC vuông tại H ta có:<mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>H</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>H</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">&#x21D2;</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>6</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>100</mn></mtd></mtr></mtable></math>" id="MathJax-Element-101-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=62+82=100<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mtable columnalign="left" columnspacing="1em" rowspacing="4pt"><mtr><mtd><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mtd></mtr><mtr><mtd><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>6</mn><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mn>8</mn><mn>2</mn></msup></mrow><mo>=</mo><mn>100</mn></mtd></mtr></mtable></math>Ta có: <mi>B</mi><mi>C</mi><mo>=</mo><mi>B</mi><mi>H</mi><mo>+</mo><mi>H</mi><mi>C</mi><mo>=</mo><mn>4</mn><mo>,</mo><mn>5</mn><mo>+</mo><mn>8</mn><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>25</mn></mrow><mn>2</mn></mfrac></math>" id="MathJax-Element-102-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.057em; padding-top: 0.477em; white-space: pre;">H<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C=4,5+8=252<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mi>�</mi><mo>=</mo><mi>�</mi><mi>�</mi><mo>+</mo><mi>�</mi><mi>�</mi><mo>=</mo><mn>4</mn><mo>,</mo><mn>5</mn><mo>+</mo><mn>8</mn><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>25</mn></mrow><mn>2</mn></mfrac></math><mo stretchy="false">&#x21D2;</mo><mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>25</mn></mrow><mn>2</mn></mfrac></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>625</mn></mrow><mn>4</mn></mfrac><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math>" id="MathJax-Element-103-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">⇒<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=(252)2=6254(1)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">⇒</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>25</mn></mrow><mn>2</mn></mfrac></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>625</mn></mrow><mn>4</mn></mfrac><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math>Ta có: <mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>225</mn></mrow><mn>4</mn></mfrac><mo>+</mo><mn>100</mn><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>625</mn></mrow><mn>4</mn></mfrac><mo stretchy="false">(</mo><mn>2</mn><mo stretchy="false">)</mo></math>" id="MathJax-Element-104-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=2254+100=6254(2)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>225</mn></mrow><mn>4</mn></mfrac><mo>+</mo><mn>100</mn><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>625</mn></mrow><mn>4</mn></mfrac><mo stretchy="false">(</mo><mn>2</mn><mo stretchy="false">)</mo></math>Từ (1) và (2) suy ra: <mi>B</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>B</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>A</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>C</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-105-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">B2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">A<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.045em; padding-top: 0.477em; white-space: pre;">C2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mi>�</mi><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math>Vậy tam giác ABC vuông tại A</div></div></div></div><div class="question c64ab750cefb726e3b384dba9" style="background-color: white; border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="question-content" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="question-content-inner" style="box-sizing: border-box; font-size: 18px; margin: 0px; max-width: 100%; padding: 0px;">Câu 25 : Một tam giác có độ dài ba đường cao là 4,8cm ; 6cm ; 8cm. Tam giác đó là tam giác gì?</div></div><ul class="dapan rows-4" style="box-sizing: border-box; flex-direction: column; justify-content: space-between; list-style: none; margin: 0px 0px 5px; padding: 0px;"><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">A<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác cân</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">B<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác vuông</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">C<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác vuông cân</div></li><li style="align-items: flex-start; box-sizing: border-box; display: flex; font-size: 18px; line-height: 26px; padding: 0px; width: 791px;"><span style="background: rgb(225, 225, 225); border-radius: 70px; box-sizing: border-box; display: inline-block; font-weight: bold; height: 26px; margin: 0px 10px 8px 0px; padding: 0px; text-align: center; top: 0px; width: 30px;">D<div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px; width: 711.9px;">Tam giác đều</div></li></ul><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;">Đáp án : B<div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div class="solution-detail-title" style="box-sizing: border-box; color: black; font-size: 18px; font-weight: bold; margin: 10px 0px; max-width: 100%; padding: 0px;">Lời giải :</div><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">Gọi a, b, c lần lượt là độ dài ba cạnh của tam giác ứng với các đường cao theo thứ tự đã cho, S là diện tích của tam giác ABC <mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mi>a</mi><mo>,</mo><mi>b</mi><mo>,</mo><mi>c</mi><mo>,</mo><mi>S</mi><mo>&gt;</mo><mn>0</mn></mrow><mo>)</mo></mrow></math>" id="MathJax-Element-106-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">a,<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">b,<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c,<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.032em; padding-top: 0.477em; white-space: pre;">S>0)<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mi>�</mi><mo>,</mo><mi>�</mi><mo>,</mo><mi>�</mi><mo>,</mo><mi>�</mi><mo>></mo><mn>0</mn></mrow><mo>)</mo></mrow></math>Ta có: <mi>S</mi><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mn>.4</mn><mo>,</mo><mn>8.</mn><mi>a</mi><mo>=</mo><mfrac><mn>1</mn><mn>6</mn></mfrac><mn>.6</mn><mo>.</mo><mi>b</mi><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mn>.8</mn><mo>.</mo><mi>c</mi></math>" id="MathJax-Element-107-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.032em; padding-top: 0.477em; white-space: pre;">S=12.4,8.<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">a=16.6.<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">b=12.8.<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mn>.4</mn><mo>,</mo><mn>8.</mn><mi>�</mi><mo>=</mo><mfrac><mn>1</mn><mn>6</mn></mfrac><mn>.6</mn><mo>.</mo><mi>�</mi><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mn>.8</mn><mo>.</mo><mi>�</mi></math> hay <mn>4</mn><mo>,</mo><mn>8</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">a</mi></mrow></mrow><mo>=</mo><mn>6</mn><mi>b</mi><mo>=</mo><mn>8</mn><mi>c</mi><mo>=</mo><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></math>" id="MathJax-Element-108-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0">4,8a=6<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">b=8<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c=2S<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>4</mn><mo>,</mo><mn>8</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">a</mi></mrow></mrow><mo>=</mo><mn>6</mn><mi>�</mi><mo>=</mo><mn>8</mn><mi>�</mi><mo>=</mo><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></math>Do đó: <mi>a</mi><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>4</mn><mo>,</mo><mn>8</mn></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>5</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>12</mn></mrow></mfrac><mo>;</mo><mi>b</mi><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></mrow><mn>6</mn></mfrac><mo>=</mo><mfrac><mi>S</mi><mn>3</mn></mfrac><mo>;</mo><mi>c</mi><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></mrow><mn>8</mn></mfrac><mo>=</mo><mfrac><mi>S</mi><mn>4</mn></mfrac></math>" id="MathJax-Element-109-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">a=2S4,8=5S12;<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">b=2S6=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.032em; padding-top: 0.477em; white-space: pre;">S3;<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c=2S8=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.032em; padding-top: 0.477em; white-space: pre;">S4<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>�</mi><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>4</mn><mo>,</mo><mn>8</mn></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>5</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>12</mn></mrow></mfrac><mo>;</mo><mi>�</mi><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></mrow><mn>6</mn></mfrac><mo>=</mo><mfrac><mi>�</mi><mn>3</mn></mfrac><mo>;</mo><mi>�</mi><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>2</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></mrow><mn>8</mn></mfrac><mo>=</mo><mfrac><mi>�</mi><mn>4</mn></mfrac></math>Ta có: <mrow class="MJX-TeXAtom-ORD"><msup><mi>b</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>c</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mfrac><mi>S</mi><mn>3</mn></mfrac></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mfrac><mi>S</mi><mn>4</mn></mfrac></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi>S</mi><mn>2</mn></msup></mrow></mrow><mn>9</mn></mfrac><mo>+</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi>S</mi><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>16</mn></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>25</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>144</mn></mrow></mfrac><mo>;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>a</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>5</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>12</mn></mrow></mfrac></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>25</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>144</mn></mrow></mfrac></math>" id="MathJax-Element-110-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">b2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c2=(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.032em; padding-top: 0.477em; white-space: pre;">S3)2+(<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.032em; padding-top: 0.477em; white-space: pre;">S4)2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.032em; padding-top: 0.477em; white-space: pre;">S29+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-right: 0.032em; padding-top: 0.477em; white-space: pre;">S216=25S2144;<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">a2=(5S12)2=25S2144<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mfrac><mi>�</mi><mn>3</mn></mfrac></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mfrac><mi>�</mi><mn>4</mn></mfrac></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mrow><mn>9</mn></mfrac><mo>+</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>16</mn></mrow></mfrac><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>25</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>144</mn></mrow></mfrac><mo>;</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mrow><mo>(</mo><mrow class="MJX-TeXAtom-ORD"><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>5</mn><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>12</mn></mrow></mfrac></mrow><mo>)</mo></mrow><mn>2</mn></msup></mrow><mo>=</mo><mfrac><mrow class="MJX-TeXAtom-ORD"><mn>25</mn><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">S</mi></mrow></mrow><mn>2</mn></msup></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mn>144</mn></mrow></mfrac></math>Suy ra <mrow class="MJX-TeXAtom-ORD"><msup><mi>a</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>b</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>c</mi><mn>2</mn></msup></mrow></math>" id="MathJax-Element-111-Frame" role="presentation" style="border: 0px; box-sizing: border-box; direction: ltr; display: inline-block; float: none; font-size: 21.06px; line-height: 0; margin: 0px; max-height: none; max-width: none; min-height: 0px; min-width: 0px; overflow-wrap: normal; padding: 1px 0px; position: relative; white-space: nowrap; word-spacing: normal;" tabindex="0"><span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">a2=<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.477em; white-space: pre;">b2+<span class="mjx-char MJXc-TeX-math-I" face="MJXc-TeX-math-I, MJXc-TeX-math-Ix, MJXc-TeX-math-Iw" style="box-sizing: content-box; display: block; padding-bottom: 0.287em; padding-top: 0.24em; white-space: pre;">c2<span class="MJX_Assistive_MathML" role="presentation" style="border: 0px; box-sizing: border-box; clip: rect(1px, 1px, 1px, 1px); display: block; font-size: 18px; height: 1px; left: 0px; line-height: 28.8px; overflow: hidden; padding: 1px 0px 0px; position: absolute; top: 0px; user-select: none; width: 1px;"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>=</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow><mo>+</mo><mrow class="MJX-TeXAtom-ORD"><msup><mi>�</mi><mn>2</mn></msup></mrow></math> nên tam giác đã cho là tam giác vuông, đỉnh góc vuông ứng với đường cao có độ dài là 4,8cm</div></div></div></div></div><div class="question c64ab750cefb726e3b384dba9" style="border-bottom: none; box-sizing: border-box; color: #262626; font-family: Roboto, sans-serif; font-size: 16px; line-height: 22px; margin: 0px; max-width: 100%;"><div class="loigiai" style="border: 2px dashed rgb(225, 225, 225); box-sizing: border-box; margin: 10px 0px; max-width: 100%; padding: 14px;"><div class="solution-detail" style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;"><div style="box-sizing: border-box; margin: 0px; max-width: 100%; padding: 0px;">
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Trắc nghiệm Toán 8 Bài 1: Định lí Pythagore Câu 1 : Tam giác ABC có AB = 3 cm, AC = 4cm, BC = 5cm. Tam giác ABC là tam giác gì? A Tam giác...

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