JCECE Engineering JCECE Engineering Solved Paper-2007

  • question_answer
    If\[\frac{dy}{dx}+y=2{{e}^{2x}}\], then\[y\]is equal to

    A) \[c{{e}^{-x}}+\frac{2}{3}{{e}^{2x}}\]

    B) \[(1+x){{e}^{-x}}+\frac{2}{3}{{e}^{2x}}+c\]

    C) \[c{{e}^{-x}}+\frac{2}{3}{{e}^{2x}}+c\]

    D) \[{{e}^{-x}}+\frac{2}{3}{{e}^{2x}}+c\]

    Correct Answer: A

    Solution :

    Given,\[\frac{dy}{dx}+y=2{{e}^{2x}}\]     \[IF={{e}^{\int{1\,\,dx}}}={{e}^{x}}\] \[\therefore \]Required solution is                 \[y(IF)=\int{2{{e}^{2x}}\cdot {{e}^{x}}\,\,dx}\] \[\Rightarrow \]                  \[y\,\,{{e}^{x}}=2\int{{{e}^{2x}}}{{e}^{x}}dx\]                            \[=2\int{{{e}^{3x}}dx}\] \[\Rightarrow \]                      \[y=\frac{2}{3}{{e}^{3x}}{{e}^{-x}}+c{{e}^{-x}}\] \[\Rightarrow \]                      \[y=\frac{2}{3}{{e}^{2x}}+c{{e}^{-x}}\]


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