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