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