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