JEE Main & Advanced Sample Paper JEE Main - Mock Test - 22

  • question_answer
    The value of the limit \[\underset{x\to 2}{\mathop{\lim }}\,\,\frac{{{e}^{3x-\,6}}-1}{\sin \,(2-x)}\] is

    A) \[\frac{3}{2}\]                        

    B)   3

    C) -3                    

    D)   -1

    Correct Answer: C

    Solution :

    \[\underset{x\to 2}{\mathop{\lim }}\,\,\frac{{{e}^{3x-6}}-1}{\sin \,(2-x)}\,\,=\,\,\underset{x\to 2}{\mathop{\lim }}\,\,\frac{{{e}^{-3(2\,-\,x)}}-1}{\sin \,(2-x)}\] Put \[2-x=t\Rightarrow x=2-t\] \[\Rightarrow \,\,\,\,\underset{t\,\to \,0}{\mathop{\lim }}\,\frac{{{e}^{-\,3t}}-1}{\sin \,\,t}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\left( \frac{0}{0}\,\,\,Form \right)\] \[=\,\,\underset{t\to 0}{\mathop{\lim }}\,\frac{(-3).e{{\,}^{-\,3t}}}{\cos \,\,t}=-\,3\]        [By L-Hospital?s rule]


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