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

  • question_answer
    If \[3{{p}^{2}}=5p+2\] and \[3{{q}^{2}}=5q+2\] where \[p\ne q\], then the equation whose roots are \[3p-2q\] and \[3q-2p\] is [Kerala (Engg.) 2005]

    A) \[3{{x}^{2}}-5x-100=0\]

    B) \[5{{x}^{2}}+3x+100=0\]

    C) \[3{{x}^{2}}-5x+100=0\]

    D) \[5{{x}^{2}}-3x-100=0\] \[5{{x}^{2}}-3x-100=0\]

    Correct Answer: A

    Solution :

    Given roots are \[3p-2q\] and\[3q-2p\]. Sum of roots = \[(3p-2q)+(3q-2p)\]= \[(p+q)=\frac{5}{3}\] Product of roots = \[(3p-2q)\,(3q-2p)\] = \[9pq-6{{q}^{2}}-6{{p}^{2}}+4pq\] = \[13pq-2(3{{p}^{2}}+3{{q}^{2}})\] = \[13\left( \frac{-2}{3} \right)-2(5p+2+5q+2)\] = \[13\,\left( \frac{-2}{3} \right)-2\left[ 5\,\left( \frac{5}{3} \right)+4 \right]\] = \[\frac{-26}{3}-2\,\left[ \frac{25}{3}+4 \right]\]= \[\frac{-100}{3}\] Hence, equation is \[3{{x}^{2}}-5x-100=\]0.


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