Bài 7: Phép Nhân Các Phân Thức Đại Số
Hướng dẫn Giải Bài 39 (Trang 52, SGK Toán 8, Tập 1)
<p>Thực hiện các phép tính sau (chú ý về dấu):</p>
<p>a) <math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mn>5</mn><mi>x</mi><mo>+</mo><mn>10</mn></mrow><mrow><mn>4</mn><mi>x</mi><mo>-</mo><mn>8</mn></mrow></mfrac><mo>.</mo><mfrac><mrow><mn>4</mn><mo>-</mo><mn>2</mn><mi>x</mi></mrow><mrow><mi>x</mi><mo>+</mo><mn>2</mn></mrow></mfrac><mo>;</mo></math> b) <math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><msup><mi>x</mi><mn>2</mn></msup><mo>-</mo><mn>36</mn></mrow><mrow><mn>2</mn><mi>x</mi><mo>+</mo><mn>10</mn></mrow></mfrac><mo>.</mo><mfrac><mn>3</mn><mrow><mn>6</mn><mo>-</mo><mi>x</mi></mrow></mfrac></math>.</p>
<p><strong>Giải </strong></p>
<p>a) <math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mn>5</mn><mi>x</mi><mo>+</mo><mn>10</mn></mrow><mrow><mn>4</mn><mi>x</mi><mo>-</mo><mn>8</mn></mrow></mfrac><mo>.</mo><mfrac><mrow><mn>4</mn><mo>-</mo><mn>2</mn><mi>x</mi></mrow><mrow><mi>x</mi><mo>+</mo><mn>2</mn></mrow></mfrac><mo>=</mo><mfrac><mrow><mfenced><mrow><mn>5</mn><mi>x</mi><mo>+</mo><mn>10</mn></mrow></mfenced><mo>.</mo><mfenced><mrow><mn>4</mn><mo>-</mo><mn>2</mn><mi>x</mi></mrow></mfenced></mrow><mrow><mfenced><mrow><mn>4</mn><mi>x</mi><mo>-</mo><mn>8</mn></mrow></mfenced><mo>.</mo><mfenced><mrow><mi>x</mi><mo>+</mo><mn>2</mn></mrow></mfenced></mrow></mfrac><mo>=</mo><mfrac><mrow><mn>5</mn><mfenced><mrow><mi>x</mi><mo>+</mo><mn>2</mn></mrow></mfenced><mo>.</mo><mn>2</mn><mfenced><mrow><mn>2</mn><mo>-</mo><mi>x</mi></mrow></mfenced></mrow><mrow><mn>4</mn><mfenced><mrow><mi>x</mi><mo>-</mo><mn>2</mn></mrow></mfenced><mo>.</mo><mfenced><mrow><mi>x</mi><mo>+</mo><mn>2</mn></mrow></mfenced></mrow></mfrac><mo>=</mo><mfrac><mrow><mn>5</mn><mfenced><mrow><mn>2</mn><mo>-</mo><mi>x</mi></mrow></mfenced></mrow><mrow><mn>2</mn><mfenced><mrow><mi>x</mi><mo>-</mo><mn>2</mn></mrow></mfenced></mrow></mfrac><mo>=</mo><mfrac><mrow><mo>-</mo><mn>5</mn><mfenced><mrow><mi>x</mi><mo>-</mo><mn>2</mn></mrow></mfenced></mrow><mrow><mn>2</mn><mfenced><mrow><mi>x</mi><mo>-</mo><mn>2</mn></mrow></mfenced></mrow></mfrac><mo>=</mo><mo>-</mo><mfrac><mn>5</mn><mn>2</mn></mfrac></math>.</p>
<p>b) <math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><msup><mi>x</mi><mn>2</mn></msup><mo>-</mo><mn>36</mn></mrow><mrow><mn>2</mn><mi>x</mi><mo>+</mo><mn>10</mn></mrow></mfrac><mo>.</mo><mfrac><mn>3</mn><mrow><mn>6</mn><mo>-</mo><mi>x</mi></mrow></mfrac><mo>=</mo><mfrac><mrow><mfenced><mrow><msup><mi>x</mi><mn>2</mn></msup><mo>-</mo><mn>36</mn></mrow></mfenced><mo>.</mo><mn>3</mn></mrow><mrow><mfenced><mrow><mn>2</mn><mi>x</mi><mo>+</mo><mn>10</mn></mrow></mfenced><mfenced><mrow><mn>6</mn><mo>-</mo><mi>x</mi></mrow></mfenced></mrow></mfrac><mo>=</mo><mfrac><mrow><mn>3</mn><mfenced><mrow><mi>x</mi><mo>-</mo><mn>6</mn></mrow></mfenced><mfenced><mrow><mi>x</mi><mo>+</mo><mn>6</mn></mrow></mfenced></mrow><mrow><mn>2</mn><mfenced><mrow><mi>x</mi><mo>+</mo><mn>5</mn></mrow></mfenced><mo>(</mo><mn>6</mn><mo>-</mo><mi>x</mi><mo>)</mo></mrow></mfrac><mo>=</mo><mfrac><mrow><mo>-</mo><mn>3</mn><mo>(</mo><mn>6</mn><mo>-</mo><mi>x</mi><mo>)</mo><mfenced><mrow><mi>x</mi><mo>+</mo><mn>6</mn></mrow></mfenced></mrow><mrow><mn>2</mn><mfenced><mrow><mi>x</mi><mo>+</mo><mn>5</mn></mrow></mfenced><mo>(</mo><mn>6</mn><mo>-</mo><mi>x</mi><mo>)</mo></mrow></mfrac><mo>=</mo><mfrac><mrow><mo>-</mo><mn>3</mn><mfenced><mrow><mi>x</mi><mo>+</mo><mn>6</mn></mrow></mfenced></mrow><mrow><mn>2</mn><mfenced><mrow><mi>x</mi><mo>+</mo><mn>5</mn></mrow></mfenced></mrow></mfrac></math></p>
Hướng dẫn Giải Bài 39 (Trang 52, SGK Toán 8, Tập 1)
GV: 
GV colearn
GV colearn
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Hướng dẫn Giải Bài 39 (Trang 52, SGK Toán 8, Tập 1)
GV: GV colearn
GV colearn