Bài 4: Những Hằng Đẳng Thức Đáng Nhớ (Tiếp)
Hướng dẫn giải Bài 26 (Trang 14 SGK Toán Đại số 8, Tập 1)
<p>Tính:</p>
<p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>a</mi><mo>)</mo><mo> </mo><msup><mrow><mo>(</mo><mn>2</mn><msup><mi>x</mi><mn>2</mn></msup><mo>+</mo><mn>3</mn><mi>y</mi><mo>)</mo></mrow><mn>3</mn></msup><mo>;</mo></math></p>
<p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>b</mi><mo>)</mo><mo> </mo><msup><mfenced><mrow><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>x</mi><mo>-</mo><mn>3</mn></mrow></mfenced><mn>3</mn></msup><mo>;</mo></math></p>
<p><strong>Giải:</strong></p>
<p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>a</mi><mo>)</mo><mo> </mo><msup><mrow><mo>(</mo><mn>2</mn><msup><mi>x</mi><mn>2</mn></msup><mo>+</mo><mn>3</mn><mi>y</mi><mo>)</mo></mrow><mn>3</mn></msup><mspace linebreak="newline"/><mo>=</mo><msup><mrow><mo>(</mo><mn>2</mn><msup><mi>x</mi><mn>2</mn></msup><mo>)</mo></mrow><mn>3</mn></msup><mo>+</mo><mn>3</mn><msup><mrow><mo>(</mo><mn>2</mn><msup><mi>x</mi><mn>2</mn></msup></mrow><mn>2</mn></msup><mo>.</mo><mn>3</mn><mi>y</mi><mo>+</mo><mn>3</mn><mo>.</mo><mn>2</mn><msup><mi>x</mi><mn>2</mn></msup><mo>.</mo><msup><mrow><mo>(</mo><mn>3</mn><mi>y</mi><mo>)</mo></mrow><mn>2</mn></msup><mo>+</mo><msup><mrow><mo>(</mo><mn>3</mn><mi>y</mi><mo>)</mo></mrow><mn>3</mn></msup><mo> </mo><mspace linebreak="newline"/><mo>=</mo><mn>8</mn><msup><mi>x</mi><mn>6</mn></msup><mo>+</mo><mn>3</mn><mo>.</mo><mn>4</mn><msup><mi>x</mi><mn>4</mn></msup><mo>.</mo><mn>3</mn><mi>y</mi><mo>+</mo><mn>3</mn><mo>.</mo><mn>2</mn><msup><mi>x</mi><mn>2</mn></msup><mo>.</mo><mn>9</mn><msup><mi>y</mi><mn>3</mn></msup><mo>+</mo><mn>27</mn><msup><mi>y</mi><mn>3</mn></msup><mspace linebreak="newline"/><mo>=</mo><mn>8</mn><msup><mi>x</mi><mn>6</mn></msup><mo>+</mo><mn>36</mn><msup><mi>x</mi><mn>4</mn></msup><mi>y</mi><mo>+</mo><mn>54</mn><msup><mi>x</mi><mn>2</mn></msup><msup><mi>y</mi><mn>3</mn></msup><mo>+</mo><mn>27</mn><msup><mi>y</mi><mn>3</mn></msup></math></p>
<p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>b</mi><mo>)</mo><mo> </mo><msup><mfenced><mrow><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>x</mi><mo>-</mo><mn>3</mn></mrow></mfenced><mn>3</mn></msup><mspace linebreak="newline"/><mo>=</mo><msup><mfenced><mrow><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>x</mi></mrow></mfenced><mn>3</mn></msup><mo>-</mo><mn>3</mn><msup><mfenced><mrow><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>x</mi></mrow></mfenced><mn>2</mn></msup><mo>.</mo><mn>3</mn><mo>+</mo><mn>3</mn><mfenced><mrow><mfrac><mn>1</mn><mn>2</mn></mfrac><mi>x</mi></mrow></mfenced><mo>.</mo><msup><mn>3</mn><mn>2</mn></msup><mo>-</mo><msup><mn>3</mn><mn>3</mn></msup><mspace linebreak="newline"/><mo>=</mo><mfrac><mn>1</mn><mn>8</mn></mfrac><msup><mi>x</mi><mn>3</mn></msup><mo>-</mo><mfrac><mn>9</mn><mn>4</mn></mfrac><msup><mi>x</mi><mn>2</mn></msup><mo>+</mo><mfrac><mn>27</mn><mn>2</mn></mfrac><mi>x</mi><mo>-</mo><mn>27</mn></math></p>
<p> </p>
Hướng dẫn Giải Bài 26 (Trang 14, SGK Toán 8, Tập 1)
GV: 
GV colearn
GV colearn
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Hướng dẫn Giải Bài 26 (Trang 14, SGK Toán 8, Tập 1)
GV: GV colearn
GV colearn