\[
\boxed{
 \left( {x}^{2}+1 \right) x{\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left( x \right) +3\, \left( 2\,{x}^{2}+1 \right) {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) -12\,y \left( x \right) =0}
\]