JEE Main & Advanced Mathematics Functions Question Bank Continuity

  • question_answer
    If \[f(x)=\,|x|\], then \[f(x)\] is [DCE 2002]

    A)            Continuous for all x

    B)            Differentiable at \[x=0\]

    C)                    Neither continuous nor differentiable at \[x=0\]

    D)            None of these

    Correct Answer: A

    Solution :

               It is obvious that \[|x|\] is continuous for all x.            Now, \[R{f}'(x)=\underset{h\to 0}{\mathop{\lim }}\,\frac{|0+h|-0}{h}=1\]            \[L{f}'(x)=\underset{h\to 0}{\mathop{\lim }}\,\frac{|0-h|-0}{-h}=-1\]            Hence \[f(x)=\,|x|\] is not differentiable at \[x=0\].


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