JEE Main & Advanced Mathematics Sequence & Series Question Bank Exponential series

  • question_answer
    \[\frac{1+\frac{{{2}^{2}}}{2\,!}+\frac{{{2}^{4}}}{3\,!}+\frac{{{2}^{6}}}{4\,!}+.....\infty }{1+\frac{1}{2\,!}+\frac{2}{3\,!}+\frac{{{2}^{2}}}{4\,!}+....\infty }=\]

    A) \[{{e}^{2}}\]

    B) \[{{e}^{2}}-1\]

    C) \[{{e}^{3/2}}\]

    D) None of these

    Correct Answer: B

    Solution :

    \[\frac{1+\frac{{{2}^{2}}}{2\ !}+\frac{{{2}^{4}}}{3\ !}+\frac{{{2}^{6}}}{4\ !}+....\infty }{1+\frac{1}{2\ !}+\frac{2}{3\ !}+\frac{{{2}^{2}}}{4\ !}+.....\infty }\] \[=\frac{\frac{1}{{{2}^{2}}}\left\{ \frac{{{2}^{2}}}{1\ !}+\frac{{{({{2}^{2}})}^{2}}}{2\ !}+\frac{{{({{2}^{2}})}^{3}}}{3\ !}+...... \right\}}{\frac{1}{{{2}^{2}}}\left\{ 2+2+\frac{{{2}^{2}}}{2\ !}+\frac{{{2}^{3}}}{3\ !}+...... \right\}}=\frac{{{e}^{({{2}^{2}})}}-1}{1+{{e}^{2}}}={{e}^{2}}-1\].


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