JEE Main & Advanced Mathematics Functions Question Bank Self Evaluation Test - Relations and Functions-I

  • question_answer
    The domain of two definition of the function \[f(x)\]is given by the equation \[{{2}^{x}}+{{2}^{y}}=2\] is

    A) \[0<x\le 1\]

    B) \[0\le x\le 1\]

    C) \[-\infty <x\le 0\]

    D)        \[-\infty <x<1\]

    Correct Answer: D

    Solution :

    [d] We have, \[{{2}^{x}}+{{2}^{y}}=2\Rightarrow {{2}^{y}}=2-{{2}^{x}}\] \[\Rightarrow y={{\log }_{2}}(2-{{2}^{x}})\Rightarrow 2-{{2}^{x}}>0\]            (\[\therefore \] y is real) \[\Rightarrow {{2}^{x}}<2\Rightarrow {{2}^{x-1}}<1\Rightarrow x-1<0\Rightarrow x<1\] \[\Rightarrow -\infty <x<1\]


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