completing the square

WordReference Random House Unabridged Dictionary of American English © 2025

complet′ing the square′, [Math.]

1. Mathematics a method, usually of solving quadratic equations, by which a quadratic expression, as x² - 4x + 3, is written as the sum or difference of a perfect square and a constant, x² - 4x + 4 + 3 - 4 = (x - 2)² - 1, by addition and subtraction of appropriate constant terms.