JEE Main & Advanced Mathematics Differential Equations Question Bank Linear defferential equations

  • question_answer
    The solution of \[\frac{dy}{dx}+y={{e}^{-x}},\,\,y(0)=0\], is [Kerala (Engg.) 2002]

    A)                 \[y={{e}^{-x}}(x-1)\]       

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

    C)                 \[y=x{{e}^{-x}}+1\]        

    D)                 \[y=x{{e}^{-x}}\]

    Correct Answer: D

    Solution :

                       \[\frac{dy}{dx}+y={{e}^{-x}}\]; I.F. \[={{e}^{\int{dx}}}={{e}^{x}}\]         \\[y{{e}^{x}}=\int{{{e}^{-x}}.{{e}^{x}}dx+c}\] Þ \[y{{e}^{x}}=x+c\]         Since \[y(0)=0\],  \ \[c=0\]                 Hence, the required solution is \[y{{e}^{x}}=x\] Þ \[y=x{{e}^{-x}}\].


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