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