Hướng dẫn Giải Bài 48 (trang 29, SGK Toán 9, Tập 1)

Hướng dẫn giải Bài 48 (Trang 29 SGK Toán 9, Tập 1)

Bài 48 (Trang 29 SGK Toán 9, Tập 1): Khử mẫu của biểu thức lấy căn (các bài 48 và 49) <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mfrac><mn>1</mn><mn>600</mn></mfrac></msqrt><mo>;</mo><mo> </mo><msqrt><mfrac><mn>11</mn><mn>540</mn></mfrac></msqrt><mo>;</mo><mo> </mo><msqrt><mfrac><mn>3</mn><mn>50</mn></mfrac></msqrt><mo>;</mo><mo> </mo><msqrt><mfrac><mn>5</mn><mn>98</mn></mfrac></msqrt><mo>;</mo><mo> </mo><msqrt><mfrac><msup><mrow><mo>(</mo><mn>1</mn><mo>-</mo><msqrt><mn>3</mn></msqrt><mo>)</mo></mrow><mn>2</mn></msup><mn>27</mn></mfrac></msqrt><mo>.</mo></math>   Hướng dẫn giải: <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mfrac><mn>1</mn><mn>600</mn></mfrac></msqrt><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>1</mn></msqrt><msqrt><mn>600</mn></msqrt></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><mn>1</mn><msqrt><mn>6</mn><mo>.</mo><msup><mn>10</mn><mn>2</mn></msup></msqrt></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><mrow><mn>1</mn><mo>.</mo><msqrt><mn>6</mn></msqrt></mrow><mrow><mn>10</mn><msqrt><mn>6</mn></msqrt><mo>.</mo><msqrt><mn>6</mn></msqrt></mrow></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>6</mn></msqrt><mn>60</mn></mfrac><mo>;</mo></math> <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mfrac><mn>11</mn><mn>540</mn></mfrac></msqrt><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>11</mn></msqrt><msqrt><mn>540</mn></msqrt></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>11</mn></msqrt><msqrt><mn>36</mn><mo>.</mo><mn>15</mn></msqrt></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><mrow><msqrt><mn>11</mn></msqrt><mo>.</mo><msqrt><mn>15</mn></msqrt></mrow><mrow><mn>6</mn><msqrt><mn>15</mn></msqrt><mo>.</mo><msqrt><mn>15</mn></msqrt></mrow></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>11</mn><mo>.</mo><mn>15</mn></msqrt><mrow><mn>6</mn><mo>.</mo><mn>15</mn></mrow></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>165</mn></msqrt><mn>90</mn></mfrac><mo>;</mo></math> <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mfrac><mn>3</mn><mn>50</mn></mfrac></msqrt><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>3</mn></msqrt><msqrt><mn>50</mn></msqrt></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>3</mn></msqrt><msqrt><mn>25</mn><mo>.</mo><mn>2</mn></msqrt></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><mrow><msqrt><mn>3</mn></msqrt><mo>.</mo><msqrt><mn>2</mn></msqrt></mrow><mrow><mn>5</mn><msqrt><mn>2</mn></msqrt><mo>.</mo><msqrt><mn>2</mn></msqrt></mrow></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>6</mn></msqrt><mn>10</mn></mfrac><mo>;</mo></math> <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mfrac><mn>5</mn><mn>98</mn></mfrac></msqrt><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>5</mn></msqrt><msqrt><mn>98</mn></msqrt></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>5</mn></msqrt><msqrt><mn>49</mn><mo>.</mo><mn>2</mn></msqrt></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><mrow><msqrt><mn>5</mn></msqrt><mo>.</mo><msqrt><mn>2</mn></msqrt></mrow><mrow><mn>7</mn><msqrt><mn>2</mn></msqrt><mo>.</mo><msqrt><mn>2</mn></msqrt></mrow></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><mn>10</mn></msqrt><mn>14</mn></mfrac><mo>;</mo></math> <math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mfrac><msup><mrow><mo>(</mo><mn>1</mn><mo>-</mo><msqrt><mn>3</mn></msqrt><mo>)</mo></mrow><mn>2</mn></msup><mn>27</mn></mfrac></msqrt><mo> </mo><mo>=</mo><mo> </mo><mfrac><msqrt><msup><mrow><mo>(</mo><mn>1</mn><mo>-</mo><msqrt><mn>3</mn></msqrt><mo>)</mo></mrow><mn>2</mn></msup></msqrt><msqrt><mn>27</mn></msqrt></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><mfenced open="|" close="|"><mrow><mn>1</mn><mo>-</mo><msqrt><mn>3</mn></msqrt></mrow></mfenced><mrow><msqrt><mn>9</mn></msqrt><mo>.</mo><mn>3</mn></mrow></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><mrow><mo>(</mo><msqrt><mn>3</mn></msqrt><mo>-</mo><mn>1</mn><mo>)</mo><mo>.</mo><msqrt><mn>3</mn></msqrt></mrow><mrow><mn>3</mn><msqrt><mn>3</mn></msqrt><mo>.</mo><msqrt><mn>3</mn></msqrt></mrow></mfrac><mo> </mo><mo> </mo><mo>=</mo><mo> </mo><mfrac><mrow><mo>(</mo><msqrt><mn>3</mn></msqrt><mo>-</mo><mn>1</mn><mo>)</mo><mo>.</mo><msqrt><mn>3</mn></msqrt></mrow><mn>9</mn></mfrac><mo> </mo><mo>(</mo><mfenced open="|" close="|"><mrow><mn>1</mn><mo>-</mo><msqrt><mn>3</mn></msqrt></mrow></mfenced><mo> </mo><mo>=</mo><mo> </mo><msqrt><mn>3</mn></msqrt><mo>-</mo><mn>1</mn><mo> </mo><mi>vì</mi><mo> </mo><msqrt><mn>3</mn></msqrt><mo> </mo><mo>></mo><mo> </mo><mn>1</mn><mo>)</mo></math>