JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Relation between roots and coefficients

  • question_answer
    Sum of roots is \[-1\] and sum of their reciprocals is \[\frac{1}{6}\], then equation is [Karnataka CET 1998]

    A) \[{{x}^{2}}+x-6=0\]

    B) \[{{x}^{2}}-x+6=0\]

    C) \[6{{x}^{2}}+x+1=0\]

    D) \[{{x}^{2}}-6x+1=0\]

    Correct Answer: A

    Solution :

    Let roots are \[\alpha \] and\[\beta \] . Given \[\alpha +\beta =-1\] \[\frac{1}{\alpha }+\frac{1}{\beta }=\frac{1}{6}\Rightarrow \frac{\alpha +\beta }{\alpha \beta }=\frac{1}{6}\Rightarrow \alpha \beta =-6\] Hence the equation, \[{{x}^{2}}-(\alpha +\beta )x+\alpha \beta =0\] Þ \[{{x}^{2}}+x-6=0\]


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