Bài 1: Tập hợp các số hữu tỉ
Hướng dẫn giải Bài 1.1 (Trang 9 SGK Toán 7, Bộ Kết nối tri thức, Tập 1)
<p><strong>Hướng dẫn giải B&agrave;i 1.1 (Trang 9 SGK To&aacute;n lớp 7 - Bộ Kết nối tri thức với cuộc sống):</strong></p> <p>Khẳng định n&agrave;o sau đ&acirc;y l&agrave; đ&uacute;ng?</p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>a</mi><mo>)</mo><mo>&#160;</mo><mn>0</mn><mo>,</mo><mn>25</mn><mo>&#160;</mo><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8474;</mi><mo>;</mo></math></p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>b</mi><mo>)</mo><mo>&#160;</mo><mo>-</mo><mfrac><mn>6</mn><mn>7</mn></mfrac><mo>&#160;</mo><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8474;</mi><mo>;</mo></math></p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>c</mi><mo>)</mo><mo>&#160;</mo><mo>-</mo><mn>235</mn><mo>&#160;</mo><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8474;</mi><mo>.</mo></math></p> <p><strong><span style="text-decoration: underline;"><em>Hướng dẫn giải:</em></span></strong></p> <p>a) Đ&uacute;ng</p> <p>Do&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mn>0</mn><mo>,</mo><mn>25</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>1</mn><mn>4</mn></mfrac><mo>,</mo><mo>&#160;</mo><mn>1</mn><mo>&#160;</mo><mi>v</mi><mi>&#224;</mi><mo>&#160;</mo><mn>4</mn><mo>&#160;</mo><mi>l</mi><mi>&#224;</mi><mo>&#160;</mo><mi>c</mi><mi>&#225;</mi><mi>c</mi><mo>&#160;</mo><mi>s</mi><mi>&#7889;</mi><mo>&#160;</mo><mi>n</mi><mi>g</mi><mi>u</mi><mi>y</mi><mi>&#234;</mi><mi>n</mi><mo>,</mo><mo>&#160;</mo><mn>4</mn><mo>&#160;</mo><mo>&#8800;</mo><mo>&#160;</mo><mn>0</mn><mo>&#160;</mo><mi>n</mi><mi>&#234;</mi><mi>n</mi><mo>&#160;</mo><mn>0</mn><mo>,</mo><mn>25</mn><mo>&#160;</mo><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8474;</mi><mo>.</mo></math></p> <p>b) Đ&uacute;ng</p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>D</mi><mi>o</mi><mo>&#160;</mo><mn>6</mn><mo>&#160;</mo><mi>v</mi><mi>&#224;</mi><mo>&#160;</mo><mn>7</mn><mo>&#160;</mo><mi>l</mi><mi>&#224;</mi><mo>&#160;</mo><mi>c</mi><mi>&#225;</mi><mi>c</mi><mo>&#160;</mo><mi>s</mi><mi>&#7889;</mi><mo>&#160;</mo><mi>n</mi><mi>g</mi><mi>u</mi><mi>y</mi><mi>&#234;</mi><mi>n</mi><mo>,</mo><mo>&#160;</mo><mn>7</mn><mo>&#160;</mo><mo>&#8800;</mo><mo>&#160;</mo><mn>0</mn><mo>&#160;</mo><mi>n</mi><mi>&#234;</mi><mi>n</mi><mo>&#160;</mo><mo>-</mo><mfrac><mn>6</mn><mn>7</mn></mfrac><mo>&#160;</mo><mo>&#160;</mo><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8474;</mi><mo>.</mo></math></p> <p>c) Sai</p> <p>Do&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>-</mo><mn>235</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mo>-</mo><mfrac><mn>235</mn><mn>1</mn></mfrac><mo>,</mo><mo>&#160;</mo><mo>-</mo><mn>235</mn><mo>&#160;</mo><mi>v</mi><mi>&#224;</mi><mo>&#160;</mo><mn>1</mn><mo>&#160;</mo><mi>l</mi><mi>&#224;</mi><mo>&#160;</mo><mi>c</mi><mi>&#225;</mi><mi>c</mi><mo>&#160;</mo><mi>s</mi><mi>&#7889;</mi><mo>&#160;</mo><mi>n</mi><mi>g</mi><mi>u</mi><mi>y</mi><mi>&#234;</mi><mi>n</mi><mo>,</mo><mo>&#160;</mo><mn>1</mn><mo>&#160;</mo><mo>&#8800;</mo><mo>&#160;</mo><mn>0</mn><mo>&#160;</mo><mi>n</mi><mi>&#234;</mi><mi>n</mi><mo>&#160;</mo><mo>-</mo><mn>235</mn><mo>&#160;</mo><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8474;</mi><mo>.</mo></math></p>
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