x^5-x^4-11x^3+11x^2+18x-18
=x^4(x-1)-11x^2(x-1)+18(x-1)
=(x-1)(x^4-11x^2+18)
=(x-1)(x^2-9)(x^2-2)
=(x-1)(x+3)(x-3)(x^2-2)(有理数范围内)
=(x-1)(x+3)(x-3)(x+√2)(x-√2)(实数范围内)