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