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