\[
\boxed{
{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) +y \left( x \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) - \left( y \left( x \right)  \right) ^{3}- \left( {\frac {{\frac {\rm d}{{\rm d}x}}f \left( x \right) }{f \left( x \right) }}+f \left( x \right)  \right)  \left( 3\,{\frac {\rm d}{{\rm d}x}}y \left( x \right) + \left( y \left( x \right)  \right) ^{2} \right) + \left( a \left( f \left( x \right)  \right) ^{2}+3\,{\frac {\rm d}{{\rm d}x}}f \left( x \right) +3\,{\frac { \left( {\frac {\rm d}{{\rm d}x}}f \left( x \right)  \right) ^{2}}{ \left( f \left( x \right)  \right) ^{2}}}-{\frac {{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}f \left( x \right) }{f \left( x \right) }} \right) y \left( x \right) +b \left( f \left( x \right)  \right) ^{3}=0}
\]