\[ y'(x) (x (a+b)+m+n)+y(x) (a b x+a n+b m)+x y''(x)=0 \] ✓ Mathematica : cpu = 0.108816 (sec), leaf count = 46
\[\left \{\left \{y(x)\to e^{-a x} \left (c_1 U(m,m+n,(a-b) x)+c_2 L_{-m}^{m+n-1}((a-b) x)\right )\right \}\right \}\]
✓ Maple : cpu = 0.112 (sec), leaf count = 39
\[ \left \{ y \left ( x \right ) ={{\rm e}^{-ax}} \left ( {{\sl M}\left (m,\,m+n,\,x \left ( a-b \right ) \right )}{\it \_C1}+{{\sl U}\left (m,\,m+n,\,x \left ( a-b \right ) \right )}{\it \_C2} \right ) \right \} \]