Bài tập cuối chương 1
Hướng dẫn giải Bài 4 (Trang 19, SGK Toán, Bộ Cánh Diều mới nhất, Tập 1)
<p><strong>B&agrave;i 4 (Trang 19, SGK To&aacute;n, Bộ C&aacute;nh diều, Tập 1)</strong></p> <p>Lập mệnh đề phủ định của mỗi mệnh đề sau:</p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>A</mi><mo>:</mo><mo>&#34;</mo><mo>&#8704;</mo><mi>x</mi><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8477;</mi><mo>,</mo><mo>|</mo><mi>x</mi><mo>|</mo><mo>&#8805;</mo><mi>x</mi><mo>&#8221;</mo><mspace linebreak="newline"/><mi>B</mi><mo>:</mo><mo>&#160;</mo><mo>&#8220;</mo><mo>&#8704;</mo><mi>x</mi><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8477;</mi><mo>,</mo><mo>&#160;</mo><mi>x</mi><mo>+</mo><mfrac><mn>1</mn><mi>x</mi></mfrac><mo>&#8805;</mo><mn>2</mn><mo>&#8221;</mo><mspace linebreak="newline"/><mi>C</mi><mo>:</mo><mo>&#160;</mo><mo>&#8220;</mo><mo>&#8707;</mo><mi>x</mi><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8484;</mi><mo>,</mo><mo>&#160;</mo><mn>2</mn><msup><mi>x</mi><mn>2</mn></msup><mo>+</mo><mn>3</mn><mi>x</mi><mo>&#8211;</mo><mn>2</mn><mo>=</mo><mn>0</mn><mo>&#8221;</mo><mspace linebreak="newline"/><mi>D</mi><mo>:</mo><mo>&#160;</mo><mo>&#8220;</mo><mo>&#8707;</mo><mi>x</mi><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8484;</mi><mo>,</mo><mo>&#160;</mo><msup><mi>x</mi><mn>2</mn></msup><mo>&#160;</mo><mo>&#60;</mo><mo>&#160;</mo><mi>x</mi><mo>&#8221;</mo><mo>.</mo><mo>&#160;</mo></math></p> <p><strong><span style="text-decoration: underline;"><em>Hướng dẫn giải:</em></span></strong></p> <p>+ Phủ định của mệnh đề&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>A</mi><mo>:</mo><mo>&#34;</mo><mo>&#8704;</mo><mi>x</mi><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8477;</mi><mo>,</mo><mo>&#160;</mo><mo>|</mo><mi>x</mi><mo>|</mo><mo>&#160;</mo><mo>&#8805;</mo><mo>&#160;</mo><mi>x</mi><mo>&#8221;</mo></math> l&agrave; mệnh đề&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><menclose notation="top"><mi>A</mi></menclose><mo>:</mo><mo>&#34;</mo><mo>&#8707;</mo><mi>x</mi><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8477;</mi><mo>,</mo><mo>&#160;</mo><mo>|</mo><mi>x</mi><mo>|</mo><mo>&#160;</mo><mo>&#8805;</mo><mo>&#160;</mo><mi>x</mi><mo>&#8221;</mo></math></p> <p>+ Phủ định của mệnh đề&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>B</mi><mo>:</mo><mo>&#160;</mo><mo>&#8220;</mo><mo>&#8704;</mo><mi>x</mi><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8477;</mi><mo>,</mo><mo>&#160;</mo><mi>x</mi><mo>&#160;</mo><mo>&#160;</mo><mo>+</mo><mfrac><mn>1</mn><mi>x</mi></mfrac><mo>&#160;</mo><mo>&#8805;</mo><mo>&#160;</mo><mn>2</mn><mo>&#8221;</mo></math> l&agrave; mệnh đề&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><menclose notation="top"><mi>B</mi></menclose><mo>:</mo><mo>&#160;</mo><mo>&#8220;</mo><mo>&#8707;</mo><mi>x</mi><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8477;</mi><mo>,</mo><mo>&#160;</mo><mi>x</mi><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mfrac><mn>1</mn><mi>x</mi></mfrac><mo>&#160;</mo><mo>&#8805;</mo><mo>&#160;</mo><mn>2</mn><mo>&#8221;</mo></math></p> <p>+ Phủ định của mệnh đề&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>C</mi><mo>:</mo><mo>&#8220;</mo><mo>&#8707;</mo><mi>x</mi><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8484;</mi><mo>,</mo><mo>&#160;</mo><mn>2</mn><msup><mi>x</mi><mn>2</mn></msup><mo>+</mo><mo>&#160;</mo><mn>3</mn><mi>x</mi><mo>&#160;</mo><mo>&#8211;</mo><mo>&#160;</mo><mn>2</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>0</mn><mo>&#8221;</mo></math> l&agrave; mệnh đề&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><menclose notation="top"><mi>C</mi></menclose><mo>:</mo><mo>&#160;</mo><mo>&#8220;</mo><mo>&#8704;</mo><mi>x</mi><mo>&#8712;</mo><mi mathvariant="normal">&#8484;</mi><mo>,</mo><mo>&#160;</mo><mn>2</mn><msup><mi>x</mi><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>3</mn><mi>x</mi><mo>&#160;</mo><mo>&#8211;</mo><mo>&#160;</mo><mn>2</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>0</mn><mo>&#34;</mo></math></p> <p>+ Phủ định của mệnh đề&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>D</mi><mo>:</mo><mo>&#160;</mo><mo>&#8220;</mo><mo>&#8707;</mo><mi>x</mi><mo>&#160;</mo><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8484;</mi><mo>,</mo><mo>&#160;</mo><msup><mi>x</mi><mn>2</mn></msup><mo>&#160;</mo><mo>&#60;</mo><mo>&#160;</mo><mi>x</mi><mo>&#34;</mo></math> l&agrave; mệnh đề&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><menclose notation="top"><mi>D</mi></menclose><mo>:</mo><mo>&#160;</mo><mo>&#8220;</mo><mo>&#8704;</mo><mi>x</mi><mo>&#160;</mo><mo>&#8712;</mo><mo>&#160;</mo><mi mathvariant="normal">&#8484;</mi><mo>,</mo><mo>&#160;</mo><msup><mi>x</mi><mn>2</mn></msup><mo>&#160;</mo><mo>&#60;</mo><mo>&#160;</mo><mi>x</mi></math>"</p>
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