x5-2x4-3x3+x2-2x-3.
=x^3(x^2-2x-3)+(x^2-2x-3)
=(x^3+1)(x^2-2x-3)
=(x+1)(x^2-x+1)(x+1)(x-3)
=(x+1)^2(x^2-2x-3)(x-3)