How do you solve the quadratic x^2+3x-28=0 using any method? Precalculus Linear and Quadratic Functions Completing the Square 1 Answer Mahendra S. ยท EZ as pi Aug 31, 2016 x= 4, -7 Explanation: x^2 +3 x -28 = 0 x^2 +7 x - 4 x -28= 0 x ( x+7 ) -4 (x + 7 ) = 0 ( x+7) ( x-4 ) = 0 Either ( x+7) = 0, or ( x-4) = 0 If x+7 = 0 x = -7 If x-7 = 0 x= 4 x = 4 , -7 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 8519 views around the world You can reuse this answer Creative Commons License