Bài 2: Căn thức bậc hai và hằng đẳng thức <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><msup><mi>A</mi><mn>2</mn></msup></msqrt><mo>=</mo><mfenced open="|" close="|"><mi>A</mi></mfenced></math>
Hướng dẫn giải Bài 9 (Trang 11 SGK Toán 9, Tập 1)
<p><strong>Bài 9 (Trang 11 SGK Toán 9, Tập 1):</strong></p>
<p>Tìm x biết:</p>
<p>a) <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><msup><mi>x</mi><mn>2</mn></msup></msqrt><mo> </mo><mo>=</mo><mo> </mo><mn>7</mn></math></p>
<p>b) <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><msup><mi>x</mi><mn>2</mn></msup></msqrt><mo> </mo><mo>=</mo><mfenced open="|" close="|"><mrow><mo>-</mo><mn>8</mn></mrow></mfenced></math></p>
<p>c) <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>4</mn><msup><mi>x</mi><mn>2</mn></msup></msqrt><mo> </mo><mo>=</mo><mo> </mo><mn>6</mn></math></p>
<p>d) <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>9</mn><msup><mi>x</mi><mn>2</mn></msup><mo> </mo></msqrt><mo> </mo><mo>=</mo><mo> </mo><mfenced open="|" close="|"><mrow><mo>-</mo><mn>12</mn></mrow></mfenced></math></p>
<p> </p>
<p><strong><span style="text-decoration: underline;"><em>Hướng dẫn giải:</em></span></strong></p>
<p>a)<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>a</mi><mo>)</mo><mo> </mo><msqrt><msup><mi>x</mi><mrow><mn>2</mn><mo> </mo></mrow></msup></msqrt><mo> </mo><mo>=</mo><mo> </mo><mn>7</mn><mo> </mo><mo>⇔</mo><mo> </mo><mfenced open="|" close="|"><mi>x</mi></mfenced><mo> </mo><mo>=</mo><mo> </mo><mn>7</mn><mo> </mo><mo>⇔</mo><mo> </mo><msub><mi>x</mi><mn>1</mn></msub><mo> </mo><mo>=</mo><mo> </mo><mn>7</mn><mo>;</mo><mo> </mo><msub><mi>x</mi><mn>2</mn></msub><mo> </mo><mo>=</mo><mo> </mo><mo>-</mo><mn>7</mn><mo>.</mo></math></p>
<p>b) <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><msup><mi>x</mi><mn>2</mn></msup></msqrt><mo> </mo><mo>=</mo><mfenced open="|" close="|"><mrow><mo>-</mo><mn>8</mn></mrow></mfenced><mo> </mo><mo>⇔</mo><msqrt><msup><mi>x</mi><mn>2</mn></msup></msqrt><mo> </mo><mo>=</mo><mo> </mo><mn>8</mn><mo> </mo><mo>⇔</mo><mfenced open="|" close="|"><mi>x</mi></mfenced><mo> </mo><mo>=</mo><mo> </mo><mn>8</mn><mo> </mo><mo>⇔</mo><mo> </mo><msub><mi>x</mi><mn>1</mn></msub><mo> </mo><mo>=</mo><mo> </mo><mn>8</mn><mo>;</mo><mo> </mo><mo> </mo><msub><mi>x</mi><mn>2</mn></msub><mo> </mo><mo>=</mo><mo> </mo><mo>-</mo><mn>8</mn><mo>.</mo></math></p>
<p>c) <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>4</mn><msup><mi>x</mi><mn>2</mn></msup></msqrt><mo> </mo><mo>=</mo><mo> </mo><mn>6</mn><mo> </mo><mo>⇔</mo><msqrt><msup><mfenced><mrow><mn>2</mn><mi>x</mi></mrow></mfenced><mn>2</mn></msup></msqrt><mo> </mo><mo>=</mo><mo> </mo><mn>6</mn><mo> </mo><mo>⇔</mo><mfenced open="|" close="|"><mrow><mn>2</mn><mi>x</mi></mrow></mfenced><mo> </mo><mo>=</mo><mo> </mo><mn>6</mn><mo> </mo><mo>⇔</mo><mo> </mo><mfenced open="|" close="|"><mi>x</mi></mfenced><mo> </mo><mo>=</mo><mo> </mo><mn>3</mn><mo> </mo><mo>⇔</mo><msub><mi>x</mi><mn>1</mn></msub><mo> </mo><mo>=</mo><mo> </mo><mn>3</mn><mo> </mo><mi>v</mi><mi>à</mi><mo> </mo><msub><mi>x</mi><mn>2</mn></msub><mo>=</mo><mo> </mo><mo>-</mo><mn>3</mn></math></p>
<p>d)<math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>9</mn><msup><mi>x</mi><mn>2</mn></msup></msqrt><mo> </mo><mo>=</mo><mo> </mo><mfenced open="|" close="|"><mrow><mo>-</mo><mn>12</mn></mrow></mfenced><mo> </mo><mo>⇔</mo><msqrt><mo> </mo><msup><mfenced><mrow><mn>3</mn><mi>x</mi></mrow></mfenced><mn>2</mn></msup></msqrt><mo> </mo><mo>=</mo><mo> </mo><mn>12</mn><mo>⇔</mo><mfenced open="|" close="|"><mrow><mn>3</mn><mi>x</mi></mrow></mfenced><mo> </mo><mo>=</mo><mo> </mo><mn>12</mn><mo> </mo><mo>⇔</mo><mfenced open="|" close="|"><mi>x</mi></mfenced><mo> </mo><mo>=</mo><mo> </mo><mn>4</mn><mo> </mo><mo>⇔</mo><msub><mi>x</mi><mn>1</mn></msub><mo> </mo><mo>=</mo><mo> </mo><mn>4</mn><mo> </mo><mi>v</mi><mi>à</mi><mo> </mo><msub><mi>x</mi><mn>2</mn></msub><mo> </mo><mo>=</mo><mo>-</mo><mn>4</mn><mo>.</mo></math></p>
Hướng dẫn Giải Bài 9 (trang 11, SGK Toán 9, Tập 1)
GV: 
GV colearn
GV colearn
Xem lời giải bài tập khác cùng bài
Video hướng dẫn giải bài tập
Hướng dẫn Giải Bài 9 (trang 11, SGK Toán 9, Tập 1)
GV: GV colearn
GV colearn