The quadratic formula
x = (−b ± √Δ) ÷ 2a, where the discriminant is Δ = b² − 4ac. If Δ is positive there are two real roots; if it is zero, one double root; if it is negative, two complex roots.
Example
x² − 5x + 6 = 0: Δ = 25 − 24 = 1, so x = (5 ± 1) ÷ 2, which gives x = 3 and x = 2. The vertex is at (2.5 ; −0.25).
Frequently asked questions
What if a is zero?
Then it is not a quadratic equation. The calculator solves the linear equation bx + c = 0 instead.
See also
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