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

  • question_answer
    The equation \[{{\log }_{e}}x+{{\log }_{e}}(1+x)=0\] can be written as [Kurukshetra CEE 1998; MP PET 1989]

    A) \[{{x}^{2}}+x-e=0\]

    B) \[{{x}^{2}}+x-1=0\]

    C) \[{{x}^{2}}+x+1=0\]

    D) \[{{x}^{2}}+xe-e=0\]

    Correct Answer: B

    Solution :

    \[{{\log }_{e}}x+{{\log }_{e}}(1+x)=0\]Þ \[{{\log }_{e}}(1+x)={{\log }_{e}}\left( \frac{1}{x} \right)\] Þ \[x(x+1)=1\,\,\Rightarrow \,\,{{x}^{2}}+x-1=0\]


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