After taking |A|=0, I am getting x3+1=0 and not x3-1=0.
Is it x3+1=0 or x3-1=0?
Ya, i missed the '-' in multiplying 2nd parameter.
BTW, expansion of (x3-1) is (x-1)(x2+x+1), so x=1, and not -1, for real values of x.
Book name : Russell and Norvig. ...