Math basics › Quadratics and polynomials
The quadratic formula
The formula
For ax² + bx + c = 0, x = (−b ± √(b² − 4ac)) / 2a. It solves every quadratic, always.
Get it to = 0 first
The formula is only true when one side is zero. Move everything across before you read off a, b and c.
The discriminant tells you the shape of the answer
b² − 4ac positive gives two real roots, zero gives one repeated root, negative gives no real roots — the parabola misses the x-axis.