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