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