How do you solve the equation #x^2+8x+16=7# by completing the square? Precalculus Linear and Quadratic Functions Completing the Square 1 Answer Kalyanam S. May 20, 2018 #color(indigo)(x = sqrt7 - 4#, #color(maroon)(x = -sqrt7 - 4# Explanation: #x^2 + 8x + 16 = 7# #(x+a)^2 = x^2 + 2ax + a^2# #:. L H S = x^2 + 2*4*x + 4^2 = (x+4)^2# Hence, #(x+4)^2 = 7# #x+4 = +- sqrt7#, taking root on both sides #color(maroon)(x = +-sqrt7 - 4# Answer link Related questions What does completing the square mean? How do I complete the square? Does completing the square always work? Is completing the square always the best method? Do I need to complete the square if #f(x) = x^2 - 6x + 9#? How do I complete the square if #f(x) = x^2 + 4x - 9#? How do I complete the square if the coefficient of #x^2# is not 1? How do I complete the square if #f(x) = 3x^2 + 12x - 9#? If I know the quadratic formula, why must I also know how to complete the square? How do I use completing the square to describe the graph of #f(x)=30-12x-x^2#? See all questions in Completing the Square Impact of this question 2309 views around the world You can reuse this answer Creative Commons License