Completing the square

Completing the square is a way to solve a quadratic equation if the equation will not factorise.

It is often convenient to write an algebraic expression as a square plus another term. The other term is found by dividing the coefficient of x by 2, and squaring it.

Any quadratic equation can be rearranged so that it can be solved in this way.

When completing the square, we end up with the form:

y=a(x\pm b)^2+c