Hướng dẫn Giải Bài 59 (trang 32, SGK Toán 9, Tập 1)

Hướng dẫn giải Bài 59 (Trang 32 SGK Toán 9, Tập 1)

Bài 59 (Trang 32 SGK Toán 9, Tập 1): <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">a</mi><mo>)</mo><mo> </mo><mn>5</mn><msqrt><mn>2</mn></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>4</mn><mi mathvariant="normal">b</mi><msqrt><mn>25</mn><msup><mi mathvariant="normal">a</mi><mn>3</mn></msup></msqrt><mo> </mo><mo>+</mo><mo> </mo><mn>5</mn><mi mathvariant="normal">a</mi><msqrt><mn>16</mn><msup><mi>ab</mi><mn>2</mn></msup></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>2</mn><msqrt><mn>9</mn><mi mathvariant="normal">a</mi></msqrt><mo>;</mo></math> <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">b</mi><mo>)</mo><mo> </mo><mn>5</mn><mi mathvariant="normal">a</mi><msqrt><mn>64</mn><msup><mi>ab</mi><mn>3</mn></msup></msqrt><mo> </mo><mo>-</mo><mo> </mo><msqrt><mn>3</mn></msqrt><mo>.</mo><msqrt><mn>12</mn><msup><mi mathvariant="normal">a</mi><mn>3</mn></msup><msup><mi mathvariant="normal">b</mi><mn>3</mn></msup></msqrt><mo> </mo><mo>+</mo><mo> </mo><mn>2</mn><mi>ab</mi><msqrt><mn>9</mn><mi>ab</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>5</mn><mi mathvariant="normal">b</mi><msqrt><mn>81</mn><msup><mi mathvariant="normal">a</mi><mn>3</mn></msup><mi mathvariant="normal">b</mi></msqrt></math>.   Hướng dẫn giải: <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">a</mi><mo>)</mo><mo> </mo><mn>5</mn><msqrt><mi mathvariant="normal">a</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>4</mn><mi mathvariant="normal">b</mi><msqrt><mn>25</mn><msup><mi mathvariant="normal">a</mi><mn>3</mn></msup></msqrt><mo> </mo><mo>+</mo><mo> </mo><mn>5</mn><mi mathvariant="normal">a</mi><msqrt><mn>16</mn><msup><mi>ab</mi><mn>2</mn></msup></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>2</mn><msqrt><mn>9</mn><mi mathvariant="normal">a</mi></msqrt><mspace linebreak="newline"/><mspace linebreak="newline"/><mo> </mo><mo>=</mo><mo> </mo><mn>5</mn><msqrt><mi mathvariant="normal">a</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>4</mn><mi mathvariant="normal">b</mi><mo>.</mo><mn>5</mn><mi mathvariant="normal">a</mi><msqrt><mi mathvariant="normal">a</mi></msqrt><mo> </mo><mo>+</mo><mo> </mo><mn>5</mn><mi mathvariant="normal">a</mi><mo>.</mo><mn>4</mn><mi mathvariant="normal">b</mi><msqrt><mi mathvariant="normal">a</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>2</mn><mo>.</mo><mn>3</mn><msqrt><mi mathvariant="normal">a</mi></msqrt><mspace linebreak="newline"/><mspace linebreak="newline"/><mo> </mo><mo>=</mo><mo> </mo><mn>5</mn><msqrt><mi mathvariant="normal">a</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>20</mn><mi>ab</mi><msqrt><mi mathvariant="normal">a</mi></msqrt><mo> </mo><mo>+</mo><mo> </mo><mn>20</mn><mi>ab</mi><msqrt><mi mathvariant="normal">a</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>6</mn><msqrt><mi mathvariant="normal">a</mi></msqrt><mo> </mo><mo>=</mo><mo> </mo><mo>-</mo><msqrt><mi mathvariant="normal">a</mi></msqrt><mo>.</mo></math>   <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">b</mi><mo>)</mo><mo> </mo><mo> </mo><mn>5</mn><mi mathvariant="normal">a</mi><msqrt><mn>64</mn><msup><mi>ab</mi><mn>3</mn></msup></msqrt><mo> </mo><mo>-</mo><mo> </mo><msqrt><mn>3</mn></msqrt><mo>.</mo><msqrt><mn>12</mn><msup><mi mathvariant="normal">a</mi><mn>3</mn></msup><msup><mi mathvariant="normal">b</mi><mn>3</mn></msup></msqrt><mo> </mo><mo>+</mo><mo> </mo><mn>2</mn><mi>ab</mi><mo>.</mo><mn>3</mn><msqrt><mi>ab</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>5</mn><mi mathvariant="normal">b</mi><mo>.</mo><mn>9</mn><mi mathvariant="normal">a</mi><msqrt><mi>ab</mi></msqrt><mspace linebreak="newline"/><mspace linebreak="newline"/><mo> </mo><mo>=</mo><mo> </mo><mn>40</mn><mi>ab</mi><msqrt><mi>ab</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><msqrt><mn>36</mn><msup><mi mathvariant="normal">a</mi><mn>3</mn></msup><msup><mi mathvariant="normal">b</mi><mn>3</mn></msup></msqrt><mo> </mo><mo>+</mo><mo> </mo><mn>6</mn><mi>ab</mi><msqrt><mi>ab</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>45</mn><mi>ab</mi><msqrt><mi>ab</mi></msqrt><mspace linebreak="newline"/><mspace linebreak="newline"/><mo> </mo><mo>=</mo><mo> </mo><mn>40</mn><mi>ab</mi><msqrt><mi>ab</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>6</mn><mi>ab</mi><msqrt><mi>ab</mi></msqrt><mo> </mo><mo>+</mo><mo> </mo><mn>6</mn><mi>ab</mi><msqrt><mi>ab</mi></msqrt><mo> </mo><mo>-</mo><mo> </mo><mn>45</mn><mi>ab</mi><msqrt><mi>ab</mi></msqrt><mspace linebreak="newline"/><mspace linebreak="newline"/><mo> </mo><mo>=</mo><mo> </mo><mo>-</mo><mn>5</mn><mi>ab</mi><msqrt><mi>ab</mi></msqrt></math>