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