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

  • question_answer
    If  \[\alpha ,\beta \]be the roots of the equation \[2{{x}^{2}}-35x+2=0\] then the value of \[{{(2\alpha -35)}^{3}}.{{(2\beta -35)}^{3}}\] is equal to [Bihar CEE 1994]

    A) 1

    B) 64

    C) 8

    D) None of these

    Correct Answer: B

    Solution :

    Since \[\alpha ,\beta \] are the roots of the equation \[2{{x}^{2}}-35x+2=0\].  Also \[\alpha \beta =1\] \[\therefore \,\,\,2{{\alpha }^{2}}-35\alpha =-2\]or \[2\alpha -35=\frac{-2}{\alpha }\] \[2{{\beta }^{2}}-35\beta =-2\]or \[2\beta -35=\frac{-2}{\beta }\] Now \[{{(2\alpha -35)}^{3}}{{(2\beta -35)}^{3}}={{\left( \frac{-2}{\alpha } \right)}^{3}}{{\left( \frac{-2}{\beta } \right)}^{3}}\]         \[=\frac{8.8}{{{\alpha }^{3}}{{\beta }^{3}}}=\frac{64}{1}=64\]


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