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