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