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

  • question_answer
    If  \[y=x-\frac{{{x}^{2}}}{2\,!}+\frac{{{x}^{3}}}{3!}-\frac{{{x}^{4}}}{4\,!}+......,\] then \[x=\]

    A) \[{{\log }_{e}}(1-y)\]

    B) \[\frac{1}{{{\log }_{e}}(1-y)}\]

    C) \[{{\log }_{e}}\frac{1}{1-y}\]

    D) \[{{\log }_{e}}(1+y)\]

    Correct Answer: C

    Solution :

    \[y=x-\frac{{{x}^{2}}}{2\ !}+\frac{{{x}^{3}}}{3\ !}-\frac{{{x}^{4}}}{4\ !}+.......=1-{{e}^{-x}}\] \[\Rightarrow {{e}^{-x}}=1-y\Rightarrow -x={{\log }_{e}}(1-y)\Rightarrow x={{\log }_{e}}\frac{1}{1-y}\].


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