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JEE Main & Advanced Sample Paper JEE Main - Mock Test - 11

  • question_answer
    If PQ is the focal chord of parabola \[{{y}^{2}}=-x\] and P is \[(-4,2),\] then the slope of tangent at Q is

    A) \[2\]     

    B) \[3\]

    C) \[4\]                 

    D) \[5\]

    Correct Answer: C

    Solution :

    [c] Tangents at the end points of focal chord are perpendicular. \[{{y}^{2}}=-x\] \[\Rightarrow \,\,\,\,2y\frac{dy}{dx}=-1\] \[\therefore \]  Slope of tangent at P, \[{{\left( \frac{dy}{dx} \right)}_{(-4,2)}}=\frac{-1}{4}\] \[\Rightarrow \]  Slope of tangent at \[Q=4\]


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