JCECE Engineering JCECE Engineering Solved Paper-2007

  • question_answer
    Let\[a,\,\,b,\,\,c\]be real, if\[a{{x}^{2}}+bx+c=0\]has two real roots \[\alpha \] and \[\beta \], where\[\alpha <-2\]and\[\beta >2\], then

    A) \[4-\frac{2b}{a}+\frac{c}{a}<0\]

    B) \[4+\frac{2b}{a}-\frac{c}{a}<0\]

    C) \[4-\frac{2b}{a}+\frac{c}{a}=0\]

    D) \[4+\frac{2b}{a}+\frac{c}{a}=0\]

    Correct Answer: A

    Solution :

    Given \[a,\,\,b,\,\,c\] are real, \[a{{x}^{2}}+bx+c=0\] has two real roots \[\alpha \] and \[\beta \] where \[\alpha <-2\] and \[\beta >2\] \[\Rightarrow \]               \[f(-2)<0\]and\[f(2)>0\] \[\Rightarrow \]               \[4a-2b+c<0\]    \[\Rightarrow \]\[4-\frac{2b}{a}+\frac{c}{a}<0\]


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