JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Self Evaluation Test - Complex Numbers and Quadratic Equations

  • question_answer
    If \[\alpha ,\beta \] are real and \[{{\alpha }^{2}},{{\beta }^{2}}\] are the roots of the equation \[{{a}^{2}}{{x}^{2}}-x+1-{{a}^{2}}=0\left( \frac{1}{\sqrt{2}}<a<1 \right)\] and \[{{\beta }^{2}}\ne 1,\] then \[{{\beta }^{2}}=\]

    A) \[{{a}^{2}}\]                          

    B) \[\frac{1-{{a}^{2}}}{{{a}^{2}}}\]

    C) \[1-{{a}^{2}}\]          

    D) \[1+{{a}^{2}}\]

    Correct Answer: B

    Solution :

    \[{{\alpha }^{2}}+{{\beta }^{2}}=\frac{1}{{{a}^{2}}}\] and \[{{\alpha }^{2}}{{\beta }^{2}}=\frac{1-{{a}^{2}}}{{{a}^{2}}}\] \[\Rightarrow \,\,{{\alpha }^{2}}+{{\beta }^{2}}-1={{\alpha }^{2}}{{\beta }^{2}}\Rightarrow ({{\alpha }^{2}}-1)({{\beta }^{2}}-1)=0\] \[\because \,\,\,\,{{\beta }^{2}}\ne 1\Rightarrow {{\alpha }^{2}}=1,\] so, \[{{\beta }^{2}}=\frac{1-{{a}^{2}}}{{{a}^{2}}}\]


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