The general solution of the differential equation $x^2+y^2-2 x y \frac{d y}{d x}=0$ is (where $C$ is a…
The general solution of the differential equation $x^2+y^2-2 x y \frac{d y}{d x}=0$ is (where $C$ is a constant of integration.)
- $2\left(x^2-y^2\right)+x=C$
- $x^2+y^2=C x$
- $x^2-y^2=C x$
- $x^2+y^2=C y$
Solution
$\begin{aligned} & x^2+y^2-2 x y \frac{d y}{d x}=0 \Rightarrow \frac{d y}{d x}=\frac{x^2+y^2}{2 x y} \Rightarrow v+x \cdot \frac{d v}{d x}=\frac{1+v^2}{2 v} \\ & \text { [Let } y=n x] \\ & \Rightarrow \int \frac{2 v d v}{1-v^2}=\int \frac{d x}{x} \\ & \Rightarrow-\log \left|1-v^2\right|+\log |c|=\log |x| \\ & \Rightarrow \log \left|\frac{c}{1-v^2}\right|=\log |x| \\ & \Rightarrow \frac{c}{1-\frac{y^2}{x^2}}=x \\ & \Rightarrow c x=x^2-y^2\end{aligned}$
Asked in: MHT CET 2022 (07 Aug Shift 1)
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