completing the square

noun

, Mathematics.

1. a method, usually of solving quadratic equations, by which a quadratic expression, as x 2 − 4 x + 3, is written as the sum or difference of a perfect square and a constant, x 2 − 4 x + 4 + 3 − 4 = ( x − 2) 2 − 1, by addition and subtraction of appropriate constant terms.