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