Let's expand the expression and simplify it:

X(x-2)(x+1) - x^2(x-1)
= X(x^2 - x - 2) - x^3 + x^2
= Xx^2 - Xx - 2X - x^3 + x^2
= Xx^2 + x^2 - Xx - x^3 - 2X
= Xx^2 + x^2 - Xx - x^3 - 2X
= (X+1)x^2 - (X+1)x - 2X
= (X+1)(x^2 - x) - 2X
= (X+1)x(x-1) - 2X
= Xx(x-1) + x(x-1) - 2X
= Xx^2 - Xx + x^2 - x - 2X
= Xx^2 + x^2 - Xx - x - 2X
= x^2(X+1) - x(X+1) - 2X
= (x^2 - x)(X+1) - 2X

Therefore, the simplified expression is:

(x^2 - x)(X + 1) - 2X = 8