\[ -a y(x)+(b-x) y'(x)+x y''(x)=0 \] ✓ Mathematica : cpu = 0.0126917 (sec), leaf count = 24
\[\{\{y(x)\to c_1 U(a,b,x)+c_2 L_{-a}^{b-1}(x)\}\}\] ✓ Maple : cpu = 0.254 (sec), leaf count = 17
\[ \left \{ y \left ( x \right ) ={\it \_C1}\,{{\sl M}\left (a,\,b,\,x\right )}+{\it \_C2}\,{{\sl U}\left (a,\,b,\,x\right )} \right \} \]