\[ -a x y(x)-b+y^{(5)}(x)=0 \] ✗ Mathematica : cpu = 0.156862 (sec), leaf count = 0
DSolve[-b - a*x*y[x] + Derivative[5][y][x] == 0,y[x],x]
, DifferentialRoot result
\[\left \{\left \{y(x)\to (x)\right \}\right \}\]
✓ Maple : cpu = 793.276 (sec), leaf count = 207155
dsolve(diff(diff(diff(diff(diff(y(x),x),x),x),x),x)-a*x*y(x)-b=0,y(x))
\[ \text {Too large to display} \]