JEE Main & Advanced Mathematics Functions Question Bank Continuity

  • question_answer
    If \[f(x)=\left\{ \begin{align}   & \frac{x}{{{e}^{1/x}}+1},\,\,\text{when}\,\,x\ne 0 \\  & \,\,\,\,\,\,\,\,\,\,\,\,\,\,0,\,\,\text{when }x=0 \\ \end{align} \right.\], then

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

    B)            \[\underset{x\to 0-}{\mathop{\lim }}\,f(x)=1\]

    C)            \[f(x)\]is continuous at\[x=0\]

    D)            None of these

    Correct Answer: C

    Solution :

               \[f(0)=0\]; \[f(0-)=\underset{h\to 0}{\mathop{\lim }}\,\,\frac{-h}{{{e}^{-1/h}}+1}=\underset{h\to 0}{\mathop{\lim }}\,\,\frac{-h}{1+\frac{1}{{{e}^{1/h}}}}=0\]            \[f(0+)=\underset{h\to 0}{\mathop{\lim }}\,\,\frac{h}{{{e}^{1/h}}+1}=0.\]


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