Ôn tập Chương I
Hướng dẫn Giải bài 12 (Trang 25, SGK Toán 10, Tập 1)
<p><strong>C&acirc;u hỏi:</strong> X&aacute;c định c&aacute;c tập hợp sau:</p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>a</mi><mo>)</mo><mo>&#160;</mo><mo>(</mo><mo>-</mo><mn>3</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mn>7</mn><mo>)</mo><mo>&#160;</mo><mo>&#8745;</mo><mo>&#160;</mo><mo>(</mo><mn>0</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mn>10</mn><mo>)</mo><mo>&#160;</mo><mo>;</mo><mspace linebreak="newline"/><mi>b</mi><mo>)</mo><mo>&#160;</mo><mo>(</mo><mo>-</mo><mo>&#8734;</mo><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mn>5</mn><mo>)</mo><mo>&#160;</mo><mo>&#8745;</mo><mo>&#160;</mo><mo>(</mo><mn>2</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mo>+</mo><mo>&#8734;</mo><mo>)</mo><mo>&#160;</mo><mo>;</mo><mspace linebreak="newline"/><mi>c</mi><mo>)</mo><mo>&#160;</mo><mi>R</mi><mo>&#160;</mo><mo>\</mo><mo>&#160;</mo><mo>(</mo><mo>-</mo><mo>&#8734;</mo><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mn>3</mn><mo>)</mo><mo>&#160;</mo><mo>.</mo></math></p> <p><strong>Lời giải:</strong></p> <p>a)&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#160;</mo><mo>(</mo><mo>-</mo><mn>3</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mn>7</mn><mo>)</mo><mo>&#160;</mo><mo>&#8745;</mo><mo>&#160;</mo><mo>(</mo><mn>0</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mn>10</mn><mo>)</mo><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mo>(</mo><mn>0</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mn>7</mn><mo>)</mo></math></p> <p>b)&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>(</mo><mo>-</mo><mo>&#8734;</mo><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mn>5</mn><mo>)</mo><mo>&#160;</mo><mo>&#8745;</mo><mo>&#160;</mo><mo>(</mo><mn>2</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mo>+</mo><mo>&#8734;</mo><mo>)</mo><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mo>(</mo><mn>2</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mn>5</mn><mo>)</mo></math></p> <p>c)&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>R</mi><mo>&#160;</mo><mo>\</mo><mo>&#160;</mo><mo>(</mo><mo>-</mo><mo>&#8734;</mo><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mn>3</mn><mo>)</mo><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mo>[</mo><mn>3</mn><mo>;</mo><mo>&#160;</mo><mo>+</mo><mo>&#8734;</mo><mo>)</mo></math></p>
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