Discriminant

The discriminant of a Quadratic Equation of the form $ax^2+bx+c=0$ is the quantity $b^2-4ac$ . When $a$ , $b$ , and $c$ are real, this is a notable quantity, because if the Discriminant is positive, the equation has two real roots; if the discriminant is negative, the equation has two non-real roots; and if the discriminant is 0, the equation has a real double root.