JEE Main & Advanced Mathematics Definite Integration Question Bank Summation of series by Definite Integration, Gamma function, Leibnitz's rule

  • question_answer
    \[\underset{x\to a}{\mathop{\lim }}\,\frac{f(x)-f(a)}{g(x)\,-g(a)},\]         [EAMCET 1994]

    A)                 \[\frac{9}{100}\]              

    B)                 \[-1/2\]

    C)                 \[\frac{1}{99}\]

    D)                 \[\frac{1}{101}\]

    Correct Answer: B

    Solution :

               \[\underset{n\to \infty }{\mathop{\lim }}\,\,\frac{{{1}^{99}}+{{2}^{99}}+.....+{{n}^{99}}}{{{n}^{100}}}=\underset{n\to \infty }{\mathop{\lim }}\,\,\sum\limits_{r=1}^{n}{\,\left( \frac{{{r}^{99}}}{{{n}^{100}}} \right)}\]                 \[=\underset{n\to \infty }{\mathop{\lim }}\,\,\frac{1}{n}\,\,\sum\limits_{r=1}^{n}{\,{{\left( \frac{r}{n} \right)}^{99}}=\int_{0}^{1}{{{x}^{99}}dx=\left[ \frac{{{x}^{100}}}{100} \right]_{0}^{1}=\frac{1}{100}.}}\]


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