Quadratic formula

Definition

A formula for solving $ax^2+bx+c=0$ : .

Specification HA18 · Paper 1, Paper 2

The quadratic formula also works when the roots are awkward fractions or surds.
Revise: Solving Quadratic Equations

1
Rearrange to $ax^2+bx+c=0$ before factorising or using the quadratic formula. Include the signs when identifying , and .

Create a free account to read GCSE Mathematics revision notes for your exam board and track your progress.

x = \frac{- b \pm b ^{2} - 4 a c}{2 a}

Used by Eduqas

0

a

b

c

2

In the quadratic formula, the whole numerator is divided by $2a$ . Use brackets carefully when entering negative coefficients into a calculator.