Using discriminant to find how many x-intercepts a quadratic has

In this video we use the discriminant, b^2-4ac, which is the 'stuff' under the square root of the quadratic formula, to find the number of x-intercepts a parabola has.
The rule is:
1. if discriminant is less than 0, parabola has no x-int
2. if discriminant is equal to 0, parabola has one x-int
3. if discriminant is greater than 0, parabola has 2 x-int