\[
\boxed{
 \left( {\frac {\rm d}{{\rm d}x}}y \left( x \right)  \right) ^{2}+a{x}^{3}{\frac {\rm d}{{\rm d}x}}y \left( x \right) -2\,a{x}^{2}y \left( x \right) =0}
\]