Carol H. answered 10/05/17
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Masters' Degree in Mathematics with 35 Years of Teaching Experience
The discriminant is b2 - 4ac, which you find from the quadratic equation: y = ax2 + bx + c.
If the discriminant > 0, there are two unequal, real roots. This means the parabola intersects the x-axis in two places.
If the discriminant = 0, there is one root of multiplicity 2. This means the parabola intersects the x-axis in one place.
If the discriminant < 0, there are no real roots. This means the parabola does not intersect the x-axis since there are two complex roots.