How do you solve the quadratic #x^2+4=0# using any method? Precalculus Linear and Quadratic Functions Completing the Square 1 Answer Shwetank Mauria Aug 26, 2016 #x=-2i# or #x=2i# Explanation: #x^2+4=0# #hArrx^2-(-4)=0# or as #i^2=-1# and hence #x^2-(2i)^2=0# or #(x+2i)(x-2i)=0# or #x+2i=0# or#x-2i=0# i.e. #x=-2i# or #x=2i# 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 1675 views around the world You can reuse this answer Creative Commons License