CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2006

  • question_answer
    The point on the curve\[y=2{{x}^{2}}-6x-4\]at which the tangent is parallel to the\[x-\]axis, is:

    A)  \[\left( \frac{3}{2},\frac{13}{2} \right)\]               

    B)  \[\left( -\frac{5}{2},-\frac{17}{2} \right)\]

    C)  \[\left( \frac{3}{2},\frac{17}{2} \right)\]

    D)         \[(0,-4)\]

    E)  \[\left( \frac{3}{2},-\frac{17}{2} \right)\]

    Correct Answer: E

    Solution :

    Tangent to any curve which is parallel to\[x-\]axis, if \[\left( \frac{dy}{dx} \right)=0\] Given     \[y=2{{x}^{2}}-6x-4\] \[\Rightarrow \]\[\frac{dy}{dx}=4x-6=0\Rightarrow x=\frac{6}{4}=\frac{3}{2}\]  \[\Rightarrow \]\[y=2.\frac{9}{4}-6.\frac{3}{2}-4\]                 \[=\frac{9}{2}-9-4=\frac{9-18-8}{2}=-\frac{17}{2}\] \[\therefore \]Required point is\[\left( \frac{3}{2},-\frac{17}{2} \right)\].


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