A function can't have x repeating any of the same number twice for example the first one (2, -2), (1, 5), (-2, 2), (1,-3), (8,-1) you have two 1's (1,5) and (1,-3) the x is the first number. Now a function can have the same y value. So your answer is (3, -1), (7,1), (-6,-1), (9,1), and (2,-1) you have to have all different x values in order for it to be a function. Hope that helps.
In the case of a quadratic equation ax2 + bx + c = 0, the discriminant is b2 − 4ac; for a cubic equation x3 + ax2 + bx + c = 0, the discriminant is a2b2 + 18abc − 4b3 − 4a3c − 27c2.