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