[[_3rd_order, _with_linear_symmetries]]
Book solution method
TO DO
Mathematica ✓
cpu = 0.0575287 (sec), leaf count = 24
Maple ✓
cpu = 0.087 (sec), leaf count = 18
DSolve[y[x] - x*y'[x] - y''[x] + x*y'''[x] == 0,y[x],x]
Mathematica raw output
{{y[x] -> x*C[1] - C[2]*Cosh[x] + I*C[3]*Sinh[x]}}
Maple raw input
dsolve(x*diff(diff(diff(y(x),x),x),x)-diff(diff(y(x),x),x)-x*diff(y(x),x)+y(x) = 0, y(x),'implicit')
Maple raw output
y(x) = _C1*x+_C2*exp(x)+_C3*exp(-x)