JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to 0}{\mathop{\lim }}\,\left( \frac{{{a}^{x}}-{{b}^{x}}}{x} \right)=\]            [EAMCET 1988; RPET 1995]

    A)                 \[\log \left( \frac{b}{a} \right)\]

    B)                 \[\log \left( \frac{a}{b} \right)\]

    C)                 \[\frac{a}{b}\]

    D)                 \[\log {{a}^{b}}\]

    Correct Answer: B

    Solution :

                       \[\underset{x\to 0}{\mathop{\lim }}\,\,\frac{{{a}^{x}}-{{b}^{x}}}{x}=\underset{x\to 0}{\mathop{\lim }}\,\,\left( \frac{{{a}^{x}}-1}{x} \right)-\underset{x\to 0}{\mathop{\lim }}\,\,\left( \frac{{{b}^{x}}-1}{x} \right)\]                                         \[=\log \,\,a-\log \,\,b=\log \,(a/b)\].


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