\[
\boxed{
{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) -3\,y \left( x \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) -3\,a \left( y \left( x \right)  \right) ^{2}-4\,{a}^{2}y \left( x \right) -b=0}
\]