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Meaning of completing the square

complet'ing the square'

Pronunciation: [key]
— Math. Math.
  1. a method, usually of solving quadratic equations, by which a quadratic expression, as x − 4x + 3, is written as the sum or difference of a perfect square and a constant, x − 4x + 4 + 3 − 4 = (x − 2) − 1, by addition and subtraction of appropriate constant terms.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.