\[
\boxed{
 \left( -{a}^{2}+{x}^{2} \right) {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) +8\,x{\frac {\rm d}{{\rm d}x}}y \left( x \right) +12\,y \left( x \right) =0}
\]