JCECE Engineering JCECE Engineering Solved Paper-2005

  • question_answer
    Solution of the equation\[x{{\left( \frac{dy}{dx} \right)}^{2}}+2\sqrt{xy}\frac{dy}{dx}+y=0\]is:

    A) \[x+y=a\]                           

    B) \[\sqrt{x}-\sqrt{y}=\sqrt{a}\]

    C) \[{{x}^{2}}+{{y}^{2}}={{a}^{2}}\]                              

    D) \[\sqrt{x}+\sqrt{y}=\sqrt{a}\]

    Correct Answer: D

    Solution :

    Given differential equation can be rewritten as                 \[{{\left( \sqrt{x}\frac{dy}{dx}+\sqrt{y} \right)}^{2}}=0\] \[\Rightarrow \]               \[\frac{dy}{\sqrt{y}}+\frac{dx}{\sqrt{x}}=0\] On integrating, we get                 \[2\sqrt{y}+2\sqrt{x}={{c}_{1}}\] \[\Rightarrow \]               \[\sqrt{x}+\sqrt{y}=\frac{{{c}_{1}}}{2}\] \[\Rightarrow \]               \[\sqrt{x}+\sqrt{y}=\sqrt{a}\]    \[\left( \text{where}\,\,a=\frac{{{c}_{1}}}{2} \right)\]


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