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JEE Main & Advanced Mathematics Applications of Derivatives Question Bank Increasing and Decreasing Function

  • question_answer
    The least value of k for which the function \[{{x}^{2}}+kx+1\]is an increasing function in the interval \[1<x<2\]is

    A)            ? 4

    B)            ? 3

    C)            ? 1

    D)            ? 2

    Correct Answer: D

    Solution :

               To be increasing, \[\frac{d}{dx}({{x}^{2}}+kx+1)>0\]\[\Rightarrow 2x+k>0\]                    For \[x\in (1,\,2)\], the least value of \[k\]is ?2.


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