\[
\boxed{
4\,{\it d4y} \left( x \right) -12\,{\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left( x \right) +11\,{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) -3\,{\frac {\rm d}{{\rm d}x}}y \left( x \right) -4\,\cos \left( x \right) =0}
\]