Bài tập cuối chương 3
Hướng dẫn giải Bài 1 (Trang 60 SGK Toán 10, Bộ Cánh diều, Tập 1)
<p><strong>B&agrave;i 1 (Trang 60 SGK To&aacute;n 10, Bộ C&aacute;nh diều, Tập 1)</strong></p> <p>T&igrave;m tập x&aacute;c định của mỗi h&agrave;m số sau:</p> <p>a)&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>y</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>1</mn><mrow><msup><mi>x</mi><mn>2</mn></msup><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><mi>x</mi></mrow></mfrac><mo>;</mo></math></p> <p>b)&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>y</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mi>x</mi><mn>2</mn></msup><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><mn>4</mn><mi>x</mi><mo>&#160;</mo><mo>+</mo><mo>&#8201;</mo><mn>3</mn></msqrt></math></p> <p>c)&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>y</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>1</mn><msqrt><mi>x</mi><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><mn>1</mn></msqrt></mfrac></math>.</p> <p><em><span style="text-decoration: underline;"><strong>Hướng dẫn giải</strong></span></em></p> <p>a) H&agrave;m số đ&atilde; cho x&aacute;c định <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#8660;</mo><mo>&#160;</mo><msup><mi>x</mi><mn>2</mn></msup><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><mi>x</mi><mo>&#160;</mo><mo>&#8800;</mo><mo>&#160;</mo><mn>0</mn><mo>&#160;</mo><mo>&#8660;</mo><mo>&#160;</mo><mfenced open="{" close=""><mtable columnalign="left"><mtr><mtd><mi>x</mi><mo>&#160;</mo><mo>&#8800;</mo><mo>&#160;</mo><mn>0</mn></mtd></mtr><mtr><mtd><mi>x</mi><mo>&#160;</mo><mo>&#8800;</mo><mo>&#160;</mo><mn>1</mn></mtd></mtr></mtable></mfenced></math></p> <p>Tập x&aacute;c định&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>D</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mi mathvariant="normal">&#8477;</mi><mo>&#160;</mo><mo>\</mo><mo>&#160;</mo><mfenced open="{" close="}"><mrow><mn>0</mn><mo>;</mo><mo>&#160;</mo><mn>1</mn></mrow></mfenced></math></p> <p>b) H&agrave;m số đ&atilde; cho x&aacute;c định&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#8660;</mo><mo>&#160;</mo><msup><mi>x</mi><mrow><mn>2</mn><mo>&#160;</mo></mrow></msup><mo>-</mo><mo>&#160;</mo><mn>4</mn><mi>x</mi><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>3</mn><mo>&#160;</mo><mo>&#8805;</mo><mo>&#160;</mo><mn>0</mn><mo>&#160;</mo><mo>&#8660;</mo><mo>&#160;</mo><mfenced open="{" close=""><mtable columnalign="left"><mtr><mtd><mi>x</mi><mo>&#160;</mo><mo>&#8805;</mo><mo>&#160;</mo><mn>3</mn></mtd></mtr><mtr><mtd><mi>x</mi><mo>&#160;</mo><mo>&#8804;</mo><mo>&#160;</mo><mn>1</mn></mtd></mtr></mtable></mfenced></math></p> <p>Tập x&aacute;c định&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>D</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mo>(</mo><mo>-</mo><mo>&#8734;</mo><mo>;</mo><mo>&#160;</mo><mn>1</mn><mo>]</mo><mo>&#160;</mo><mo>&#8746;</mo><mo>&#160;</mo><mo>[</mo><mn>3</mn><mo>;</mo><mo>&#160;</mo><mo>+</mo><mo>&#8734;</mo><mo>)</mo></math></p> <p>c) H&agrave;m số đ&atilde; cho x&aacute;c định&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#8660;</mo><mo>&#160;</mo><mi>x</mi><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><mn>1</mn><mo>&#160;</mo><mo>&#62;</mo><mo>&#160;</mo><mn>0</mn><mo>&#160;</mo><mo>&#8660;</mo><mo>&#160;</mo><mi>x</mi><mo>&#160;</mo><mo>&#62;</mo><mo>&#160;</mo><mn>1</mn></math>.</p> <p>Tập x&aacute;c định&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>D</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mo>(</mo><mn>1</mn><mo>;</mo><mo>&#160;</mo><mo>+</mo><mo>&#8734;</mo><mo>)</mo></math></p>
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