JEE Main & Advanced Mathematics Limits, Continuity and Differentiability Question Bank Mock Test - Continuity and Differentiability

  • question_answer
    The function \[f(x)=\frac{{{({{3}^{x}}-1)}^{2}}}{\sin x\cdot \ln \,(1+x)},x\ne 0\], is continuous at x=0. Then the value of f(0) is

    A) \[2{{\log }_{e}}3\]        

    B) \[{{(2{{\log }_{e}}3)}^{2}}\]

    C) \[{{\log }_{e}}6\]          

    D) none of these

    Correct Answer: B

    Solution :

    [b] Given f(x) is continuous at x=0. Therefore, \[\underset{x\to 0}{\mathop{\lim }}\,f(x)=f(0)\] Or  \[\underset{x\to 0}{\mathop{\lim }}\,\frac{{{({{3}^{x}}-1)}^{2}}}{\sin x\,\ln (1+x)}=f(0)\] Or  \[f(0)=\underset{x\to 0}{\mathop{\lim }}\,\frac{{{\left( \frac{{{3}^{x}}-1}{x} \right)}^{2}}}{\left( \frac{\sin x}{x} \right)\left( \frac{\ln (1+x)}{x} \right)}={{(ln3)}^{2}}\]


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