Discriminant
The quantity b² − 4ac inside the quadratic formula. Determines how many real roots a quadratic has.
Definition
For ax² + bx + c = 0: if b² − 4ac > 0 there are two real roots; if b² − 4ac = 0 there is one repeated root; if b² − 4ac < 0 there are no real roots.
Example
x² + 5x + 6 = 0. b² − 4ac = 25 − 24 = 1 > 0, so two real roots.
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