Question: Let (C \subset \mathbb{ZxZ} ) be the set of integer pairs ((a,b)) for which the three complex roots (r_1,r_2,r_3) of the polynomial (p(x)=x^3-2x^2+ax-b) satisfy (r_1^3+r_2^3+r_3^3=0). Then the cardinality of (C) is A. (\infty) B. 0 C. 1 D. (1<|C|<\infty) Discussion: We have (r_1+r_2+r_3=-(-2)=2) (r_1r_2+r_2r_3+r_3r_1=a) and (r_1r_2r_3=-(-b)=b) Also, of the top of our head, we […]