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

  • question_answer
    If \[\alpha ,\beta \] are the roots of the quadratic equation \[{{x}^{2}}+bx-c=0\], then the equation whose roots are \[b\]and  \[c\] is [Pb. CET 1989]

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

    B)   \[{{x}^{2}}-[(\alpha +\beta )+\alpha \beta ]x-\alpha \beta (\alpha +\beta )=0\]

    C) \[{{x}^{2}}+[(\alpha +\beta )+\alpha \beta ]x+\alpha \beta (\alpha +\beta )=0\]

    D) \[{{x}^{2}}+[\alpha \beta +(\alpha +\beta )]x-\alpha \beta (\alpha +\beta )=0\]

    Correct Answer: C

    Solution :

    \[\alpha +\beta =-\]b and \[\alpha \beta =-c\] Now \[b+c=-[(\alpha +\beta )+\alpha \beta ],bc=(\alpha +\beta )(\alpha \beta )\] Hence required equation is \[{{x}^{2}}+[(\alpha +\beta )+\alpha \beta ]x+\alpha \beta (\alpha +\beta )=0\].


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