JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to 0}{\mathop{\lim }}\,\frac{x{{e}^{x}}-\log (1+x)}{{{x}^{2}}}\] equals [RPET 1996]

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

    B)                 \[\frac{1}{3}\]

    C)                 \[\frac{1}{2}\]

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

    Correct Answer: D

    Solution :

                       Let \[y=\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{x\,{{e}^{x}}-\log \,(1+x)}{{{x}^{2}}}\], \[\left( \frac{0}{0}\,\text{form} \right)\]            Applying L-Hospital's rule,            \[y=\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{{{e}^{x}}+x\,{{e}^{x}}-\frac{1}{1+x}}{2x}\], \[\left( \frac{0}{0}\,\text{form} \right)\]            \[y=\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{1}{2}\,\left[ {{e}^{x}}+{{e}^{x}}+x\,{{e}^{x}}+\frac{1}{{{(1+x)}^{2}}} \right]\]                 \[y=\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{1}{2}\,[1+1+0+1]=\frac{3}{2}\].


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