\[ y'(x) (x (a+b)+m+n)+y(x) (a b x+a n+b m)+x y''(x)=0 \] ✓ Mathematica : cpu = 0.0651933 (sec), leaf count = 51
\[\left \{\left \{y(x)\to c_1 e^{-a x} U(m,m+n,(a-b) x)+c_2 e^{-a x} L_{-m}^{m+n-1}((a-b) x)\right \}\right \}\] ✓ Maple : cpu = 0.374 (sec), leaf count = 39
\[ \left \{ y \left ( x \right ) ={{\rm e}^{-ax}} \left ( {{\sl U}\left (m,\,m+n,\, \left ( a-b \right ) x\right )}{\it \_C2}+{{\sl M}\left (m,\,m+n,\, \left ( a-b \right ) x\right )}{\it \_C1} \right ) \right \} \]