If $y=y_1(x)$ and $y=y_2(x)$ are two solutions of equation $\frac{d^{2}y}{d{x}^2}+P(x)\frac{dy}{dx}+Q(x)y=0$ then show that $y_1(\frac{d{y}_2}{dx})-y_2(\frac{d{y}_1}{dx})=c{e}^{-{\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}Pdx},$ where $c$ is constant