Question

Complete the square on the following quadratic x^2+18x+7=0 what value is added to both sides of the equation.

Answer 1

x^2 + 18x + 7 = 0
x^2 + 18x = -7
x^2 + 18x + 81 = -7 + 81....add 81 to both sides
(x + 9)^2 = 74
x + 9 = sqrt 74
x = -9 (+-) sqrt 74

x = -9 + sqrt 74
x = -9 - sqrt 74

the reason u add 81 to both sides.....u take half of the x term, then square it.
half of 18 is 9....9^2 = 81