How do you solve the quadratic #x^2-2x-8=0# using any method? Precalculus Linear and Quadratic Functions Completing the Square 1 Answer Alan P. Sep 8, 2016 #x in {-2,4}# Explanation: #x^2-2x-8=0# can be factored as #color(white)("XXX")(x+2)(x-4)=0# which implies either #color(white)("XXX")x+2=0color(white)("XX")rarrcolor(white)("XX")x=-2# or #color(white)("XXX")x-4=0color(white)("XX")rarrcolor(white)("XX")x=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 1895 views around the world You can reuse this answer Creative Commons License