JEE Main & Advanced Mathematics Applications of Derivatives Question Bank Self Evaluation Test - Application of Derivatives

  • question_answer
    Let \[f:[a,b]\to R\] be a function such that for \[c\in (a,b),f'(c)=f'(c)=f'''(c)={{f}^{iv}}(c)={{f}^{v}}(c)=0\]. Then

    A) f has a local extremum at x = c

    B) f has neither local maximum nor minimum at x = c

    C) f is necessarily a constant function

    D) it is difficult to say whether or (b)

    Correct Answer: D

    Solution :

    [d] For \[f(x)={{x}^{6}}\] and \[f(x)={{x}^{7}},\,\,f'(0)=f''(0)=f'''(0)\] \[={{f}^{iv}}(0)={{f}^{v}}(0)=0\]. \[x=0\] is point of minima for \[f(x)={{x}^{6}}\]. But \[x=0\] is not point of maxima/minima for \[f(x)={{x}^{7}}\]. Hence, it is difficult to say anything.


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