CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2006

  • question_answer
    The solution of the differential equation \[x\frac{dy}{dx}+2y={{x}^{2}}\]is:

    A)  \[y=\frac{{{x}^{2}}+c}{4{{x}^{2}}}\]                        

    B)  \[y=\frac{{{x}^{2}}}{4}+c\]

    C)  \[y=\frac{{{x}^{4}}+c}{{{x}^{2}}}\]          

    D)  \[y=\frac{{{x}^{4}}+c}{4{{x}^{2}}}\]

    E)  \[y=\frac{{{x}^{3}}}{4}+\frac{c}{{{x}^{2}}}\]

    Correct Answer: D

    Solution :

    \[x=\frac{dy}{dx}+2y={{x}^{2}}\] On differentiating w.r.t\[x,\]we get \[\frac{dy}{dx}+\frac{2}{x}y=x\] Integrating factor\[={{e}^{\int{\frac{2}{x}dx}}}={{x}^{2}}\] \[\therefore \]Required solution is \[y.{{x}^{2}}=\int{{{x}^{3}}}dx=\frac{{{x}^{4}}}{4}+c=\frac{{{x}^{4}}+c}{4}\] \[\therefore \]  \[y=\frac{{{x}^{4}}+c}{4{{x}^{2}}}\]


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