\[
\boxed{
{\frac {\rm d}{{\rm d}x}}y \left( x \right) ={\frac {-4\,xy \left( x \right) -{x}^{3}-2\,a{x}^{2}-4\,x+8}{8\,y \left( x \right) +2\,{x}^{2}+4\,ax+8}}=0}
\]