Bài 3: Liên hệ giữa phép nhân và phép khai phương
Hướng dẫn giải Bài 18 (Trang 14 SGK Toán 9, Tập 1)
<p><strong>B&agrave;i 18 (Trang 14 SGK To&aacute;n 9, Tập 1):</strong></p> <p>&Aacute;p dụng quy tắc nh&acirc;n c&aacute;c căn bậc hai, h&atilde;y t&iacute;nh</p> <p><span class="mce-nbsp-wrap" contenteditable="false"><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">a</mi><mo>)</mo><mo>&#160;</mo><msqrt><mn>7</mn></msqrt><mo>.</mo><msqrt><mn>63</mn></msqrt><mo>;</mo><mspace linebreak="newline"/><mspace linebreak="newline"/><mi mathvariant="normal">b</mi><mo>)</mo><mo>&#160;</mo><msqrt><mn>2</mn><mo>,</mo><mn>5</mn></msqrt><mo>.</mo><msqrt><mn>30</mn></msqrt><mo>.</mo><msqrt><mn>48</mn></msqrt><mo>;</mo><mspace linebreak="newline"/><mspace linebreak="newline"/><mi mathvariant="normal">c</mi><mo>)</mo><mo>&#160;</mo><msqrt><mn>0</mn><mo>,</mo><mn>4</mn></msqrt><mo>.</mo><msqrt><mn>6</mn><mo>,</mo><mn>4</mn></msqrt><mo>&#160;</mo><mo>;</mo><mspace linebreak="newline"/><mspace linebreak="newline"/><mi mathvariant="normal">d</mi><mo>)</mo><mo>&#160;</mo><msqrt><mn>2</mn><mo>,</mo><mn>7</mn></msqrt><mo>.</mo><msqrt><mn>5</mn></msqrt><mo>.</mo><msqrt><mn>1</mn><mo>,</mo><mn>5</mn></msqrt></math>&nbsp;&nbsp;&nbsp;</span></p> <p>&nbsp;</p> <p><strong><span style="text-decoration: underline;"><em>Hướng dẫn giải:</em></span></strong></p> <p><sub><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>a</mi><mo>)</mo><mo>&#160;</mo><msqrt><mn>7</mn></msqrt><mo>.</mo><msqrt><mn>63</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>7</mn><mo>.</mo><mn>63</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>7</mn><mn>2</mn></msup><mo>.</mo><msup><mn>3</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>7</mn><mn>2</mn></msup></msqrt><mo>.</mo><msqrt><msup><mn>3</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>7</mn><mo>.</mo><mn>3</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>21</mn><mo>.</mo><mspace linebreak="newline"/><mspace linebreak="newline"/><mi>b</mi><mo>)</mo><mo>&#160;</mo><msqrt><mn>2</mn><mo>,</mo><mn>5</mn></msqrt><mo>.</mo><msqrt><mn>30</mn></msqrt><mo>.</mo><msqrt><mn>48</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>2</mn><mo>,</mo><mn>5</mn><mo>.</mo><mn>30</mn><mo>.</mo><mn>48</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>60</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>60</mn><mo>.</mo><mspace linebreak="newline"/><mspace linebreak="newline"/><mi>c</mi><mo>)</mo><mo>&#160;</mo><msqrt><mn>0</mn><mo>,</mo><mn>4</mn></msqrt><mo>.</mo><msqrt><mn>6</mn><mo>,</mo><mn>4</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>0</mn><mo>,</mo><mn>4</mn><mo>.</mo><mn>6</mn><mo>,</mo><mn>4</mn></msqrt><mo>&#160;</mo><mo>&#160;</mo><mo>=</mo><msqrt><mn>0</mn><mo>,</mo><mn>04</mn></msqrt><mo>.</mo><msqrt><mn>64</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>0</mn><mo>,</mo><mn>2</mn><mo>.</mo><mn>8</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>1</mn><mo>,</mo><mn>6</mn><mo>.</mo><mspace linebreak="newline"/><mspace linebreak="newline"/><mi>d</mi><mo>)</mo><mo>&#160;</mo><msqrt><mn>2</mn><mo>,</mo><mn>7</mn></msqrt><mo>.</mo><msqrt><mn>5</mn></msqrt><mo>.</mo><msqrt><mn>1</mn><mo>,</mo><mn>5</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>2</mn><mo>,</mo><mn>7</mn><mo>.</mo><mn>5</mn><mo>.</mo><mn>1</mn><mo>,</mo><mn>5</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>3</mn><mn>2</mn></msup><mo>.</mo><mn>1</mn><mo>,</mo><msup><mn>5</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>3</mn><mo>.</mo><mn>1</mn><mo>,</mo><mn>5</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>4</mn><mo>,</mo><mn>5</mn><mo>.</mo></math></sub></p>
Xem lời giải bài tập khác cùng bài