JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    If \[\underset{x\to 0}{\mathop{\lim }}\,\frac{\log (3+x)\,-\log (3-x)}{x}=k,\,\] then the value of k is [AIEEE 2003]

    A)                 0

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

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

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

    Correct Answer: C

    Solution :

                       \[\underset{x\to 0}{\mathop{\lim }}\,\frac{\log (3+x)-\log (3-x)}{x}=k\]                 By L-Hospital?s rule,  \[\underset{x\to 0}{\mathop{\lim }}\,\frac{\frac{1}{3+x}+\frac{1}{3-x}}{1}=k\]  Þ \[\frac{2}{3}=k\].


You need to login to perform this action.
You will be redirected in 3 sec spinner