JEE Main & Advanced Sample Paper JEE Main - Mock Test - 2

  • question_answer
    A particular solution of \[\log \,\left( \frac{dy}{dx} \right)=3x+4y,\] \[y(0)=0\] is

    A) \[{{e}^{3x}}+3{{e}^{-4y}}=4\]

    B) \[4{{e}^{3x}}-3{{e}^{-4y}}=3\]

    C) \[3{{e}^{3x}}+4{{e}^{4y}}=7\]

    D) \[4{{e}^{3x}}+3{{e}^{-4y}}=7\]

    Correct Answer: D

    Solution :

    Given differential equation is \[\log \left( \frac{dy}{dx} \right)=3x+4y,\] \[y(0)=0\] \[\Rightarrow \,\,\frac{dy}{dx}={{e}^{3x+4y}}={{e}^{3x}}.{{e}^{4y}}\]\[\Rightarrow \int{{{e}^{-4y}}dy=\int{{{e}^{3x}}dx}}\]\[\Rightarrow \,\,\frac{{{e}^{-4y}}}{-4}=\frac{{{e}^{3x}}}{3}+c\] By using \[y=0\] when \[x=0,\]we get \[c=-\frac{7}{12}\] \[\therefore \]  Particular solution is \[4{{e}^{3x}}+3{{e}^{-4y}}=7\]


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