10th Class Mathematics Related to Competitive Exam Question Bank Algebra

  • question_answer
    If the roots of \[{{x}^{2}}-2mx+{{m}^{2}}-1=0\]lie between - 2 and 4, then

    A)  \[-3\le m\le 4\]

    B)  \[-3\le m\le 5\]

    C)  \[-1\le m\le 5\]  

    D)  \[-1\le m\le 3\]

    Correct Answer: C

    Solution :

                    \[{{x}^{2}}-2mx+{{m}^{2}}-1=0\] or            \[x=\frac{2m\pm \sqrt{4{{m}^{2}}-4({{m}^{2}}-1)}}{2}\]                    \[=\frac{2m\pm 2}{2}\]                    \[=m\pm 1\] Since, the roots lie between \[-2\] and\[4\], therefore                 \[-2\le m\pm 1\le 4\] or            \[-3\le m\le 3\] and        \[-1\le m\le 5\]


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