Quadratic formula - GCSE Maths Definition

The quadratic formula is one method that can be used to solve quadratic equations, which are, or can be rearranged to be, of the form

ax² + bx + c = 0

In this equation, a, b, and c are constants (numbers), and x is the (unknown) variable. The quadratic formula allows us to find the value(s) of x that satisfy the equation. The quadratic formula is

The "±" ("plus, minus") symbol in the formula usually results in there being two value(s) of x that satisfy the equation. One value (solution) for x comes from adding the square root part, the other from subtracting it. The quadratic formula can be used to solve any quadratic equation but is usually used when either factorising, or completing the square, is awkward. If your calculator has a function to solve quadratic equations, it is probably programmed to do so by using the quadratic formula. In GCSE Mathematics, the quadratic formula is often needed to find solutions to a quadratic equation to a required number of decimal places or significant figures.