BCECE Engineering BCECE Engineering Solved Paper-2015

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

    A) \[\log \left( \frac{x}{y} \right)=\frac{1}{x}+\frac{1}{y}+C\]

    B) \[\log \left( \frac{y}{x} \right)=\frac{1}{x}+\frac{1}{y}+C\]

    C) \[\log \left( xy \right)=\frac{1}{x}+\frac{1}{y}+C\]

    D) \[\log (xy)+\frac{1}{x}+\frac{1}{y}=C\]

    Correct Answer: A

    Solution :

    The given differential, equation is \[{{x}^{2}}(1-y)\frac{dy}{dx}+{{y}^{2}}(1+x)=0\] \[\Rightarrow \]               \[{{x}^{2}}(1-y)dy+{{y}^{2}}(1+x)dx=0\] \[\Rightarrow \]               \[\frac{1-y}{{{y}^{2}}}dy+\frac{1+x}{{{x}^{2}}}dx=0\] On integrating, we get \[-\frac{1}{y}-\log y-\frac{1}{x}+\log x=C\] \[\Rightarrow \]               \[\log \left( \frac{x}{y} \right)=\frac{1}{x}+\frac{1}{y}+C\]


You need to login to perform this action.
You will be redirected in 3 sec spinner