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