\[
\boxed{
{\frac {\rm d}{{\rm d}x}}y \left( x \right) =1/4\,{\frac {-{x}^{2}+1+4\,{x}^{3}\sqrt {{x}^{2}-2\,x+1+8\,y \left( x \right) }}{1+x}}=0}
\]