\[
\boxed{
 \left( \sin \left( x \right) +x \right) {\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left( x \right) +3\, \left( \cos \left( x \right) +1 \right) {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) -3\,\sin \left( x \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) -y \left( x \right) \cos \left( x \right) +\sin \left( x \right) =0}
\]