JEE Main & Advanced Mathematics Differentiation Question Bank Self Evaluation Test - Limits and Derivatives

  • question_answer
    The value of \[\underset{x\to 0}{\mathop{\lim }}\,\frac{{{({{4}^{x}}-1)}^{3}}}{\sin \frac{{{x}^{2}}}{4}\log (1+3x)},\] is

    A) \[\frac{4}{3}{{(in4)}^{2}}\]

    B) \[\frac{4}{3}{{(In4)}^{3}}\]

    C) \[\frac{3}{2}{{(In4)}^{2}}\]

    D) \[\frac{3}{2}{{(In4)}^{3}}\]

    Correct Answer: B

    Solution :

    [b] \[\underset{x\to 0}{\mathop{\lim }}\,\frac{{{({{4}^{x}}-1)}^{3}}}{\sin \frac{{{x}^{2}}}{4}\log (1+3x)}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{{{({{4}^{x}}-1)}^{3}}}{{{x}^{3}}}.\frac{{{(x/2)}^{2}}}{\sin {{x}^{2}}/4}.\frac{3x}{\log (1+3x)}.\frac{4}{3}\] \[=\frac{4}{3}{{(lo{{g}_{e}}4)}^{3}}.1.{{\log }_{e}}(e)=\frac{4}{3}{{(lo{{g}_{e}}4)}^{3}}.\]


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