JEE Main & Advanced Mathematics Functions Question Bank Continuity

  • question_answer
    If \[f(x)=\left\{ \begin{align}   & 1+{{x}^{2}},\,\,\,\text{when}\,0\le x\le 1 \\  & 1-x\,\,\,,\text{when}\,\,x>1 \\ \end{align} \right.\],  then

    A)            \[\underset{x\to {{1}^{+}}}{\mathop{\lim }}\,f(x)\ne 0\]           

    B)  \[\underset{x\to {{1}^{-}}}{\mathop{\lim }}\,f(x)\ne 2\]

    C)  \[f(x)\]is discontinuous at \[x=1\]

    D)            None of these

    Correct Answer: C

    Solution :

               \[\underset{x\to 1+}{\mathop{\lim }}\,f(x)=0\]and  \[=\underset{h\to 0}{\mathop{\lim }}\,\,\,h\,\,\frac{{{e}^{1/h}}-{{e}^{-1/h}}}{{{e}^{1/h}}+{{e}^{-1/h}}}\]            Hence \[f(x)\] is discontinuous at \[x=1\].


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