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CLAT Sample Paper CLAT Sample Paper-5

  • question_answer
    If \[(-4)\] is a root of the quadratic equation \[{{x}^{2}}-px-4=0\] and the quadratic equation \[{{x}^{2}}-px+k=0\] has equal roots, find the value of k.

    A)  \[\frac{9}{4}\]

    B)  1

    C)  2.5

    D)  3

    Correct Answer: A

    Solution :

    Since, (-4) is a root of \[{{x}^{2}}-px-4=0\]. Sine, both the roots of this equation are equal. \[\therefore \] Sum of the roots \[(\alpha +\alpha )2\alpha =-3\] \[\Rightarrow \] \[\alpha =\frac{-3}{2}\] \[\therefore \] Product of t roots \[(\alpha \cdot \alpha )={{\alpha }^{2}}\] \[=\,\left( -\frac{3}{2} \right)=\frac{9}{4}=k\] \[\therefore \] \[k=\frac{9}{4}\]


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