How do you get a quadratic equation from its x-intercepts?

Answer 1

For the purpose of this discussion, you should consider the terms "x-intercepts," "roots," "solutions" and "zeroes" to be interchangeable. Let's take a couple of random x- intercepts, -3 and 5. For those to have been the solutions, they had to have come from (x + 3) and (x - 5) respectively. If you multiply them together, you'll get the quadratic equation x2 - 2x - 15
Essentially, what we've done here is the factoring process backwards.