JCECE Engineering JCECE Engineering Solved Paper-2003

  • question_answer
    A solution of the differential equation\[{{\left( \frac{dy}{dx} \right)}^{2}}-x\frac{dy}{dx}+y=0\]is:

    A) \[y=2\]

    B) \[y=2x\]

    C) \[y=2x-4\]

    D) \[y=2{{x}^{2}}-4\]

    Correct Answer: C

    Solution :

    Given differential equation is                 \[{{\left( \frac{dy}{dx} \right)}^{2}}-x\frac{dy}{dx}+y=0\] Let          \[\frac{dy}{dx}=p\] \[\therefore \]  \[{{p}^{2}}-px+y=0\] On differentiating w.r.t. x, we get                 \[2p\frac{dp}{dx}-p-x\frac{dp}{dx}+\frac{dy}{dx}=0\] \[\Rightarrow \]               \[\frac{dp}{dx}(2p-x)=0\]                             \[\left[ \because \,\,\frac{dy}{dx}=p \right]\] \[\Rightarrow \]               \[\frac{dp}{dx}=0\] On integrating, we get                 \[p=c\] \[\Rightarrow \]               \[\frac{dy}{dx}=0\] On integrating, we get                                 \[y=cx-{{c}^{2}}\] If\[c=2\], then   \[y=2x-4\]


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