\[ x y^{(3)}(x) (a x+b)+(\alpha x+\beta ) y''(x)-f(x)+x y'(x)+y(x)=0 \] ✓ Mathematica : cpu = 2.67415 (sec), leaf count = 56731
DSolve[-f[x] + y[x] + x*Derivative[1][y][x] + (beta + alpha*x)*Derivative[2][y][x] + x*(b + a*x)*Derivative[3][y][x] == 0,y[x],x]
\[ \text {Too large to display} \] ✓ Maple : cpu = 0.783 (sec), leaf count = 1213
dsolve((a*x+b)*x*diff(diff(diff(y(x),x),x),x)+(alpha*x+beta)*diff(diff(y(x),x),x)+x*diff(y(x),x)+y(x)-f(x)=0,y(x))
\[\text {Expression too large to display}\]