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JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Solution of quadratic inequations and Miscellaneous equations

  • question_answer
    The number of roots of the equation \[\log (-2x)\] \[=2\log (x+1)\] are [AMU 2001]

    A) 3

    B) 2

    C) 1

    D) None of these

    Correct Answer: B

    Solution :

    Given, \[\log (-2x)=2\log (x+1)\] \[\Rightarrow -2x={{(x+1)}^{2}}\]      \[\Rightarrow {{x}^{2}}+4x+1=0\] Þ \[x=\frac{-4\pm \sqrt{16-4}}{2}\] Þ \[x=\frac{-4\pm \sqrt{12}}{2}\] Þ \[x=-2\pm \sqrt{3}\]Þ \[x=(-2+\sqrt{3}),(-2-\sqrt{3})\].


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