Bài 4: Liên hệ giữa phép chia và phép khai phương
Hướng dẫn giải Bài 36 (Trang 20 SGK Toán 9, Tập 1)
<p><strong>B&agrave;i 36 (Trang 20 SGK To&aacute;n 9, Tập 1):</strong></p> <p>Mỗi khẳng định sau đ&acirc;y đ&uacute;ng hay sai? V&igrave; sao?</p> <p>a)&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mn>0</mn><mo>,</mo><mn>01</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>0</mn><mo>,</mo><mn>0001</mn></msqrt><mo>;</mo></math></p> <p>b)&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>-</mo><mn>0</mn><mo>,</mo><mn>5</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mo>-</mo><mn>0</mn><mo>,</mo><mn>25</mn></msqrt><mo>;</mo></math></p> <p>c)&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>39</mn></msqrt><mo>&#160;</mo><mo>&#60;</mo><mo>&#160;</mo><mn>7</mn><mo>&#160;</mo><mi>v&#224;</mi><mo>&#160;</mo><msqrt><mn>39</mn></msqrt><mo>&#160;</mo><mo>&#62;</mo><mo>&#160;</mo><mn>6</mn><mo>;</mo></math></p> <p>d)&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>(</mo><mn>4</mn><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msqrt><mn>13</mn></msqrt><mo>)</mo><mo>.</mo><mn>2</mn><mi>x</mi><mo>&#160;</mo><mo>&#60;</mo><mo>&#160;</mo><msqrt><mn>3</mn></msqrt><mfenced><mrow><mn>4</mn><mo>-</mo><msqrt><mn>13</mn></msqrt></mrow></mfenced><mo>&#160;</mo><mo>&#8660;</mo><mo>&#160;</mo><mn>2</mn><mi>x</mi><mo>&#160;</mo><mo>&#60;</mo><mo>&#160;</mo><msqrt><mn>3</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>a) Khẳng định n&agrave;y đ&uacute;ng v&igrave;&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mn>0</mn><mo>,</mo><mn>0001</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>0</mn><mo>,</mo><msup><mn>01</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>0</mn><mo>,</mo><mn>01</mn></math></p> <p>b) Khẳng định n&agrave;y sai v&igrave; vế phải kh&ocirc;ng c&oacute; nghĩa&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mfenced><mrow><msqrt><mi>X</mi></msqrt><mo>&#160;</mo><mi>c</mi><mi>&#243;</mi><mo>&#160;</mo><mi>n</mi><mi>g</mi><mi>h</mi><mi>&#297;</mi><mi>a</mi><mo>&#160;</mo><mi>k</mi><mi>h</mi><mi>i</mi><mo>&#160;</mo><mi>X</mi><mo>&#160;</mo><mo>&#8805;</mo><mo>&#160;</mo><mn>0</mn></mrow></mfenced></math></p> <p>c) Khẳng định n&agrave;y đ&uacute;ng v&igrave;&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mn>7</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>7</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>49</mn></msqrt><mo>&#160;</mo><mo>&#62;</mo><mo>&#160;</mo><msqrt><mn>39</mn></msqrt></math></p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mn>6</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>6</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>36</mn></msqrt><mo>&#160;</mo><mo>&#60;</mo><mo>&#160;</mo><msqrt><mn>39</mn></msqrt></math></p> <p>d) Khẳng định n&agrave;y đ&uacute;ng v&igrave;&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mn>4</mn><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msqrt><mn>13</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>4</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msqrt><mn>13</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>16</mn></msqrt><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msqrt><mn>13</mn></msqrt><mo>&#160;</mo><mo>&#62;</mo><mo>&#160;</mo><mn>0</mn></math></p> <p>Do vậy&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mfenced><mrow><mn>4</mn><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msqrt><mn>13</mn></msqrt></mrow></mfenced><mo>.</mo><mn>2</mn><mi>x</mi><mo>&#160;</mo><mo>&#60;</mo><mo>&#160;</mo><msqrt><mn>3</mn></msqrt><mfenced><mrow><mn>4</mn><mo>-</mo><msqrt><mn>13</mn></msqrt></mrow></mfenced><mo>&#160;</mo><mfenced><mrow><mi>c</mi><mi>h</mi><mi>i</mi><mi>a</mi><mo>&#160;</mo><mn>2</mn><mo>&#160;</mo><mi>v</mi><mi>&#7871;</mi><mo>&#160;</mo><mi>c</mi><mi>h</mi><mi>o</mi><mo>&#160;</mo><mn>4</mn><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msqrt><mn>13</mn></msqrt></mrow></mfenced></math></p> <p>Ta được bất phương tr&igrave;nh trở th&agrave;nh&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#8660;</mo><mo>&#160;</mo><mn>2</mn><mi>x</mi><mo>&#160;</mo><mo>&#60;</mo><mo>&#160;</mo><msqrt><mn>3</mn></msqrt></math>.</p>
Hướng dẫn Giải Bài 36 (trang 19, SGK Toán 9, Tập 1)
GV: GV colearn
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Hướng dẫn Giải Bài 36 (trang 19, SGK Toán 9, Tập 1)
GV: GV colearn