JEE Main & Advanced Mathematics Limits, Continuity and Differentiability Question Bank Mock Test - Continuity and Differentiability

  • question_answer
    If \[f(x)=\left\{ \begin{matrix}    x+2,\,\,\,\,\,\,\,\,\,x<0  \\    -{{x}^{2}}-2,\,\,\,\,\,\,0\le x<1  \\    x,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\ge 1  \\ \end{matrix} \right.\], Then the number, of points of discontinuity of \[\left| f(x) \right|\]is

    A) 1                     

    B) 2

    C) 3                     

    D) none of these

    Correct Answer: A

    Solution :

    [a] \[f(x)=\left\{ \begin{matrix}    x+2,  \\    -{{x}^{2}}-2,  \\    x,  \\ \end{matrix} \right.\begin{matrix}    x<0  \\    \,\,\,\,0\le x<1  \\    x\ge 1  \\ \end{matrix}\] \[\therefore \,\,\,\,\left| f(x) \right|=\left\{ \begin{matrix}    -x-2,  \\    x+2,  \\    {{x}^{2}}+2,  \\    x,  \\ \end{matrix} \right.\,\,\,\begin{matrix}    x<-2  \\    \,\,\,\,-2\le x<0  \\    \,\,\,0\le x<1  \\    x\ge 1  \\ \end{matrix}\] It is discontinuous at x=1. Therefore, number of discontinuity is 1.


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