JEE Main & Advanced JEE Main Paper Phase-I Held on 07-1-2020 Morning

  • question_answer
    If \[y=y(x)\] is the solution of the differential equation, \[{{e}^{y}}\left( \frac{dy}{dx}-1 \right)={{e}^{x}}\] such that \[y(0)=0,\]then \[y(1)\] is equal to [JEE MAIN Held on 07-01-2020 Morning]

    A) 2e                    

    B) \[lo{{g}_{e}}2\]

    C) \[2+lo{{g}_{e}}2\]       

    D) \[1+lo{{g}_{e}}2\]

    Correct Answer: D

    Solution :

    [d]
    \[{{e}^{y}}=t\]
    \[{{e}^{y}}\frac{dy}{dx}=\frac{dt}{dx}\]
    \[\Rightarrow \frac{dt}{dx}-t={{e}^{x}}\]
    \[I.F.={{e}^{\int{-1dx}}}={{e}^{-x}}\]
    \[\Rightarrow t.{{e}^{-x}}=x+c\]
    \[{{e}^{y-x}}=x+c\]
    \[c=1\]
    \[\Rightarrow f(1)=1+\ln \,\,2\]


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