Quadratic Formula

Key points

The quadratic formula is a formula used to find the roots/zeroes/solutions of the parabola.
- Used when other forms of algebraic solution are not feasible.
Used with the coefficients of the quadratic equation in standard form.

The Quadratic Formula is one of the most common ways to solve a quadratic equation, used to find the x-intercepts.

Use it when you cannot factor, complete the square, or solve algebraically.
It uses the variables a, b, and c. These correspond to the coefficients of the quadratic in standard form: ax^2+bx+c=0
- Make sure to convert to standard form before using it.
Quadratics have two solutions – this is the role of the plus/minus sign in the equation.
- Once you simplify the radical expression, split the equation up into two equations – one where you add it, and the other where you subtract it.
The example to the right shows that factoring and using the quadratic formula yield the same results.