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