there is an equation$\displaystyle (p(x)y')'+q(x)y=0$ when p(x) and q(x) are deferentiable

on I.

$\displaystyle y_{1}(x)=u$ $\displaystyle y_{2}=\frac{1}{u(x)}$

y1 and y2 are two independant solutions of a given equation.

show that u(x) makes a first order differential equation