text: how do you complete the square? in quadratic formula? in solving algebra way you take the coefficient of the x term, divide it by 2 and then square it.  then add and subtract this number. x^2 + 6x - 13  the coefficient of x is -6 -6/2 = -3 (-3)^2 = 9 thus, add and subtract 9 (x^2 - 6x + 9) -13 - 9 = (x-3)^2 - 22  if the coefficient of x^2 is not one extra steps must be done. example: 2x^2 + 20x - 5  put 2x^2 + 20x in parentheses (2x^2 + 20x) - 5  factor a 2 from the parentheses 2(x^2 + 10x) - 5   divide the coefficient of x by 2 and then square it.  add and subtract this number inside the parentheses. 10/2 = 5 5^2 = 25 2(x^2 + 10x) - 5 = 2(x^2 + 10x + 25 - 25) - 5   take the -25 out from parentheses.  when you do this multiply the -25 by the number on the outside of the parentheses. 2(x^2 + 10x + 25 - 25) - 5 = 2(x^2 + 10x + 25) -25(2) - 5 = 2(x+5)^2 - 50 - 5 = 2(x+5)^2 - 55 if you can complete the square, then you do not need to use the quadratic formula.