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