JEE Main & Advanced Mathematics Functions Question Bank Functions

  • question_answer
    If \[f(x)=\frac{x}{1+x}\], then \[{{f}^{-1}}(x)\] is equal to [AMU 1999]

    A)                    \[\frac{(1+x)}{x}\]

    B)            \[\frac{1}{(1+x)}\]

    C)                    \[\frac{(1+x)}{(1-x)}\]

    D)            \[\frac{x}{(1-x)}\]

    Correct Answer: D

    Solution :

               \[f(x)=\frac{x}{1+x}\]. Let \[y=f(x)\Rightarrow x={{f}^{-1}}(y)\]            \ \[y=\frac{x}{1+x}\Rightarrow y+yx=x\] Þ \[x=\frac{y}{1-y}\]            Þ \[{{f}^{-1}}(y)=\frac{y}{1-y}\] Þ \[{{f}^{-1}}(x)=\frac{x}{1-x}\].


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