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