Bài 8: Rút gọn biểu thức chứa căn thức bậc hai
Hướng dẫn giải Bài 58 (Trang 32 SGK Toán 9, Tập 1)
<p><strong>B&agrave;i 58 (Trang 32 SGK To&aacute;n 9, Tập 1):</strong></p> <p>R&uacute;t gọn c&aacute;c biểu thức sau:</p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">a</mi><mo>)</mo><mo>&#160;</mo><mn>5</mn><msqrt><mfrac><mn>1</mn><mn>5</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><msqrt><mn>20</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>5</mn></msqrt><mo>;</mo></math></p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">b</mi><mo>)</mo><mo>&#160;</mo><msqrt><mfrac><mn>1</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>4</mn><mo>,</mo><mn>5</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>12</mn><mo>,</mo><mn>5</mn></msqrt><mo>.</mo></math></p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">c</mi><mo>)</mo><mo>&#160;</mo><msqrt><mn>20</mn></msqrt><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msqrt><mn>45</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>3</mn><msqrt><mn>8</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>72</mn></msqrt><mo>;</mo></math></p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">d</mi><mo>)</mo><mo>&#160;</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>.</mo><msqrt><mn>200</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#8201;</mo><mn>2</mn><mo>.</mo><msqrt><mn>0</mn><mo>,</mo><mn>08</mn></msqrt><mo>.</mo><msqrt><mn>50</mn></msqrt><mo>.</mo></math></p> <p>&nbsp;</p> <p><strong><span style="text-decoration: underline;"><em>Hướng dẫn giải:</em></span></strong></p> <p><strong><span style="text-decoration: underline;"><em><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">a</mi><mo>)</mo><mo>&#160;</mo><mn>5</mn><msqrt><mfrac><mn>1</mn><mn>5</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><msqrt><mn>20</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>5</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>5</mn><mn>2</mn></msup><mo>.</mo><mfrac><mn>1</mn><mn>5</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mfrac><mn>1</mn><msup><mn>2</mn><mn>2</mn></msup></mfrac><mo>.</mo><mn>20</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>5</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>5</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>5</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>5</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>3</mn><msqrt><mn>5</mn></msqrt><mo>.</mo></math></em></span></strong></p> <p><strong><span style="text-decoration: underline;"><em><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">b</mi><mo>)</mo><mo>&#160;</mo><msqrt><mfrac><mn>1</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>4</mn><mo>,</mo><mn>5</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>12</mn><mo>,</mo><mn>5</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mfrac><mn>1</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mfrac><mn>9</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mfrac><mn>25</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mfrac><mn>1</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><msup><mn>3</mn><mn>2</mn></msup><mo>.</mo><mfrac><mn>1</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><msup><mn>5</mn><mn>2</mn></msup><mo>.</mo><mfrac><mn>1</mn><mn>2</mn></mfrac></msqrt><mspace linebreak="newline"/><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mfrac><mn>1</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>3</mn><msqrt><mfrac><mn>1</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>5</mn><msqrt><mfrac><mn>1</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>9</mn><msqrt><mfrac><mn>1</mn><mn>2</mn></mfrac></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>9</mn><mfrac><msqrt><mn>1</mn></msqrt><msqrt><mn>2</mn></msqrt></mfrac><mspace linebreak="newline"/><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>9</mn><mfrac><msqrt><mn>2</mn></msqrt><mrow><msqrt><mn>2</mn></msqrt><mo>.</mo><msqrt><mn>2</mn></msqrt></mrow></mfrac><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>9</mn><mn>2</mn></mfrac><msqrt><mn>2</mn></msqrt><mo>.</mo></math></em></span></strong></p> <p><strong><span style="text-decoration: underline;"><em><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">c</mi><mo>)</mo><mo>&#160;</mo><msqrt><mn>20</mn></msqrt><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msqrt><mn>45</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>3</mn><msqrt><mn>18</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>72</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>4</mn><mo>.</mo><mn>5</mn></msqrt><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msqrt><mn>9</mn><mo>.</mo><mn>5</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>3</mn><msqrt><mn>9</mn><mo>.</mo><mn>2</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msqrt><mn>36</mn><mo>.</mo><mn>2</mn></msqrt><mspace linebreak="newline"/><mo>=</mo><mo>&#160;</mo><mn>2</mn><msqrt><mn>5</mn></msqrt><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><mn>3</mn><msqrt><mn>5</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>9</mn><msqrt><mn>2</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>6</mn><msqrt><mn>2</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mo>-</mo><msqrt><mn>5</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>15</mn><msqrt><mn>5</mn></msqrt><mo>.</mo></math></em></span></strong></p> <p><strong><span style="text-decoration: underline;"><em><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">d</mi><mo>)</mo><mo>&#160;</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>.</mo><msqrt><mn>200</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>2</mn><mo>.</mo><msqrt><mn>0</mn><mo>,</mo><mn>08</mn></msqrt><mo>.</mo><msqrt><mn>50</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>.</mo><msqrt><mn>100</mn><mo>.</mo><mn>2</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>2</mn><msqrt><mfrac><mn>8</mn><mn>100</mn></mfrac></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>0</mn><mo>,</mo><mn>4</mn><mo>.</mo><msqrt><mn>25</mn><mo>.</mo><mn>2</mn></msqrt><mspace linebreak="newline"/><mo>=</mo><mo>&#160;</mo><msqrt><mn>2</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>2</mn><mo>.</mo><mfrac><msqrt><mn>2</mn></msqrt><msqrt><mn>10</mn></msqrt></mfrac><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>2</mn><msqrt><mn>2</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>2</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>0</mn><mo>,</mo><mn>4</mn><msqrt><mn>2</mn></msqrt><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>2</mn><msqrt><mn>2</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>3</mn><msqrt><mn>2</mn></msqrt><mo>.</mo></math></em></span></strong></p>
Hướng dẫn Giải Bài 58 (trang 32, SGK Toán 9, Tập 1)
GV: GV colearn
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Hướng dẫn Giải Bài 58 (trang 32, SGK Toán 9, Tập 1)
GV: GV colearn