JEE Main & Advanced JEE Main Paper (Held On 15 April 2018) Slot-II

  • question_answer
    Let \[f(x)=\left\{ \begin{align}   & {{(x-1)}^{\frac{1}{2-x}}},x>1,x\ne 2k, \\  & x=2 \\ \end{align} \right.\] The value of \[k\] for which \[f\] is continuous at \[x=2\] is          [JEE Online 15-04-2018 (II)]

    A)         \[{{e}^{-2}}\]                                    

    B) \[e\]     

    C) \[{{e}^{-1}}\]                    

    D)          \[1\]

    Correct Answer: C

    Solution :

    If \[f(x)\] is continuous at \[x=2\] , then \[\underset{x\to 2}{\mathop{\lim }}\,{{(x-1)}^{\frac{1}{2x}}}=k\] Above is  \[{{1}^{\infty }}\]form, \[\therefore k={{e}^{1}}\] Where \[l=\underset{x\to 2}{\mathop{\lim }}\,(x-1-1)\times \frac{1}{2-x}=\underset{x\to 2}{\mathop{\lim }}\,\frac{x-2}{2-x}=-1\] \[\Rightarrow k={{e}^{-1}}\]


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