CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2005

  • 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:

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

    B)  \[5{{x}^{2}}+3x+100=0\]

    C)  \[3{{x}^{2}}-5x+100=0\]

    D)  \[3{{x}^{2}}+5x-100=0\]

    E)  \[5{{x}^{2}}-3x-100=0\]

    Correct Answer: A

    Solution :

    \[\because \]\[3{{p}^{2}}=5p+2\] \[\Rightarrow \]               \[p=2,-\frac{1}{3}\] and     \[3{{q}^{2}}=5q+2\] \[\Rightarrow \]               \[q=2,-\frac{1}{3}\] \[\because \]     \[p\ne q,\] \[\therefore \]  assume that \[p=2\]and \[q=-\frac{1}{3}\] Now, the given roots of equation are \[(3p-2q)\]and\[(3q-2p)\]i.e., \[\left( \frac{20}{3},-5 \right)\] Sum of roots\[=\frac{20}{3}-5=\frac{5}{3}\] and product of roots\[=\frac{20}{3}\times (-5)=-\frac{100}{3}\] \[\therefore \]Required equation is                 \[{{x}^{2}}-\frac{5}{3}x-\frac{100}{3}=0\] \[\Rightarrow \]               \[3{{x}^{2}}-5x-100=0\]


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