JEE Main & Advanced JEE Main Paper (Held On 12-Jan-2019 Morning)

  • question_answer
    If\[x>1\]for\[{{(2x)}^{2y}}=4{{e}^{2x-2y}},\]then\[{{(1+lo{{g}_{e}}2x)}^{2}}\frac{dy}{dx}\]equals [JEE Main Online Paper Held On 12-Jan-2019 Morning]

    A) \[\frac{x\,{{\log }_{e}}2x-{{\log }_{e}}2}{x}\]               

    B) \[{{\log }_{e}}2x\]

    C) \[\frac{x\,{{\log }_{e}}2x+{{\log }_{e}}2}{x}\]             

    D) \[x\,{{\log }_{e}}2x\]

    Correct Answer: A

    Solution :

    \[{{(2x)}^{2y}}=4{{e}^{2x-2y}}\] \[\Rightarrow \]\[2y{{\log }_{e}}2x={{\log }_{e}}4+2x-2y\] \[\Rightarrow \]\[2y{{\log }_{e}}2x=2{{\log }_{e}}2+2x-2y\] \[\Rightarrow \]\[y{{\log }_{e}}2x={{\log }_{e}}2+x-y\Rightarrow y=\frac{x+{{\log }_{e}}2}{1+{{\log }_{e}}2x}\] \[\therefore \]\[\frac{dy}{dx}=\frac{1+{{\log }_{e}}2x-(x+lo{{g}_{e}}2)\frac{1}{x}}{{{(1+lo{{g}_{e}}2x)}^{2}}}\] \[\Rightarrow \]\[\frac{dy}{dx}={{(1+lo{{g}_{e}}2x)}^{2}}=\frac{x{{\log }_{e}}2x-{{\log }_{e}}2}{x}\]


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