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