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