JEE Main & Advanced AIEEE Solved Paper-2002

  • question_answer
    If \[{{x}^{y}}={{e}^{x-y}}\], then \[\frac{dy}{dx}\] is   AIEEE  Solved  Paper-2002

    A) \[\frac{1+x}{1+\log x}\]   

    B)                           \[\frac{1-\log x}{{{(1+\log x)}^{2}}}\]         

    C)           not defined       

    D)           \[\frac{\log x}{{{(1+\log x)}^{2}}}\]

    Correct Answer: D

    Solution :

    \[\because \,\,{{x}^{y}}={{e}^{x-y}}\] Taking log on both sides, we get                    \[y\log x=(x-y){{\log }_{e}}e\] \[\Rightarrow \]   \[y=\frac{x}{1+\log x}\] On differentiating w.r.t. x, we get                    \[\frac{dy}{dx}=\frac{(1+\log x)-x.\frac{1}{x}}{(1+\log {{x}^{2}})}\]                    \[=\frac{\log x}{{{(1+\log x)}^{2}}}\]


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