JEE Main & Advanced JEE Main Paper (Held On 15 April 2018) Slot-II

  • question_answer
    Let \[\int_{{}}^{{}}{:A\to }B\] be a function defined as \[\int_{{}}^{{}}{(x)}=\frac{x-1}{x-2}\], where\[A=R-\{2\}\] and \[B=R\{1\}\]. Then \[\int_{{}}^{{}}{{}}\] is                                             [JEE Online 15-04-2018 (II)]

    A)         Invertible and \[{{f}^{-1}}(y)=\frac{2y+1}{y-1}\]

    B) Invertible and \[{{f}^{-1}}(y)=\frac{3y+1}{y-1}\]

    C) No invertible

    D) Invertible and \[{{f}^{-1}}(y)=\frac{2y-1}{y-1}\]

    Correct Answer: D

    Solution :

    Let \[y=f(x)\] \[\Rightarrow y=\frac{x-1}{x-2}\] \[\Rightarrow yx-2y=x-1\] \[\Rightarrow (y-1)x=2y-1\] \[\Rightarrow x={{f}^{-1}}(y)=\frac{2y-1}{y-1}\] So on the given domain the function is invertible and its inverse can be computed as shown above. So, option D is the correct answer.


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