JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to \infty }{\mathop{\lim }}\,\,{{\left( \frac{x+a}{x+b} \right)}^{x+b}}=\] [EAMCET 2001]

    A)                 1

    B)                 \[{{e}^{b-a}}\]

    C)                 \[{{e}^{a-b}}\]

    D)                 \[{{e}^{b}}\]

    Correct Answer: C

    Solution :

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


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