\[
\boxed{
{\frac {\rm d}{{\rm d}x}}y \left( x \right) = \left( y \left( x \right)  \right) ^{3}+{x}^{2} \left( y \left( x \right)  \right) ^{2}+1/3\,y \left( x \right) {x}^{4}+1/27\,{x}^{6}-2/3\,x=0}
\]