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