JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to \infty }{\mathop{\lim }}\,{{\left( 1-\frac{4}{x-1} \right)}^{3x-1}}=\] [Karnataka CET 2004]

    A)                 \[{{e}^{12}}\]

    B)                 \[{{e}^{-12}}\]

    C)                 \[{{e}^{4}}\]

    D)                 \[{{e}^{3}}\]

    Correct Answer: B

    Solution :

                       \[\underset{x\to \infty }{\mathop{\lim }}\,{{\left( 1-\frac{4}{x-1} \right)}^{3x-1}}=\underset{x\to \infty }{\mathop{\lim }}\,{{\left[ {{\left( 1+\frac{(-4)}{x-1} \right)}^{\left( \frac{x-1}{-4} \right)}} \right]}^{\left( \frac{-4}{x-1} \right)(3x-1)}}\]                                                                    \[={{e}^{\underset{x\to \infty }{\mathop{\lim }}\,\left[ \frac{-4\left( 3-\frac{1}{x} \right)}{\left( 1-\frac{1}{x} \right)} \right]}}={{e}^{-12}}\].


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