One Algebraic Approach
When C = 0, 1, or 2, the discriminant is negative and therefore there are no values of A.
When C = -4, for example:
Therefore one INTEGER solution to the simultaneous equations is A = 1, B = -1, and C = -4.
Examine other values of C. How do you conclude that there are no integer solution for C > 0 or C < -4? How do you determine there are exactly 3 integer solutions?