JEE Main & Advanced Mathematics Differentiation Question Bank Differentiation of implicit function Parametric

  • question_answer
    If \[{{2}^{x}}+{{2}^{y}}={{2}^{x+y}}\], then \[\frac{dy}{dx}=\]        [MP PET 1995; AMU 2000]

    A)            \[{{2}^{x-y}}\frac{{{2}^{y}}-1}{{{2}^{x}}-1}\]

    B)            \[{{2}^{x-y}}\frac{{{2}^{y}}-1}{1-{{2}^{x}}}\]

    C)            \[\frac{{{2}^{x}}+{{2}^{y}}}{{{2}^{x}}-{{2}^{y}}}\]

    D)            None of these

    Correct Answer: B

    Solution :

               On differentiating \[{{2}^{x}}\log 2+{{2}^{y}}\log 2.\frac{dy}{dx}\]            \[={{2}^{x}}{{.2}^{y}}\frac{dy}{dx}.\log 2+{{2}^{y}}{{.2}^{x}}\log 2\]            Þ  \[{{2}^{x}}+{{2}^{y}}\frac{dy}{dx}={{2}^{x+y}}\frac{dy}{dx}+{{2}^{x+y}}\]            Þ  \[\frac{dy}{dx}=\frac{{{2}^{x+y}}-{{2}^{x}}}{{{2}^{y}}-{{2}^{x+y}}}={{2}^{x-y}}\frac{{{2}^{y}}-1}{1-{{2}^{x}}}\].


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