(x-1)^3+(x-1)^2+(x-1)
=(x-1)[(x-1)^2+(x-1)+1]
=(x-1)[(x^2-2x+1)+x-1+1]
=(x-1)(x^2-2x+1+x-1+1)
=(x-1)(x^2-2x-x+1-1+1)
=(x-1)(x^2-x+1)
=(x-1)x0
=0