sum and product not working for cubic

Question

When doing sum and product of 0, -3, 2 the resulting quadratic is y=x^3+x^2-13x. The problem is that when we graphed it, it didn't pass through the zeros. Is there any reason for this? Nobody in my class or the teacher could figure out why. Does sum and product have restrictions or is there something else going on.

Answer 1

you must expand $$x(x+3)(x-2)$$