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

  • question_answer
    If \[f(x)=\left\{ \begin{align}   & \left( {{x}^{2}}/a \right)-a,\,\,when\,\,\,x<0 \\  & 0,\,\,when\,\,\,x=a,\,\,then \\  & a-\left( {{x}^{2}}/a \right),\,\,when\,\,x>a \\ \end{align} \right.\]

    A) \[\underset{x\to a}{\mathop{\lim }}\,f(x)=a\]

    B) \[f(x)\] is continuous at x = a

    C) \[f(x)\] is discontinuous at x = a

    D) None of these

    Correct Answer: B

    Solution :

    [b] \[f(a)=0\] \[\underset{x\to a-}{\mathop{\lim }}\,f(x)=\underset{x\to a-}{\mathop{\lim }}\,\left( \frac{{{x}^{2}}}{a}-a \right)=\underset{h\to 0}{\mathop{\lim }}\,\left\{ \frac{{{\left( a-h \right)}^{2}}}{a}-a \right\}=0\] and \[\underset{x\to a+}{\mathop{\lim }}\,f(x)=\underset{h\to 0}{\mathop{\lim }}\,\left\{ a-\frac{{{\left( a+h \right)}^{2}}}{a} \right\}=0\] Hence it is continuous at \[x=a\].


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