\[ y'(x) (x (a+b)+m+n)+y(x) (a b x+a n+b m)+x y''(x)=0 \] ✓ Mathematica : cpu = 0.0556294 (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 = 0.09 (sec), leaf count = 39
\[y \relax (x ) = {\mathrm e}^{-a x} \left (\KummerM \left (m , m +n , x \left (a -b \right )\right ) c_{1}+\KummerU \left (m , m +n , x \left (a -b \right )\right ) c_{2}\right )\]