How do you use completing the square method to solve 4x^2+5x=-1?

1 Answer
Mar 24, 2018

x =-1/4
x=-1

Explanation:

4x^2+5x=-1

4x^2+5x+1=0

(2x)^2+5x+1=0

(2x)^2+2×(2x)×(5/4)+(5/4)^2-(5/4)^2+1=0

(2x+5/4)^2 -(5/4)^2+1=0

(2x+5/4)^2 =25/16-1

(2x+5/4)^2 =9/16

2x+5/4=+-sqrt(9/16)

2x+5/4=3/4 or 2x+5/4=-3/4

2x=3/4-5/4 or 2x= -3/4-5/4

2x=-2/4 or 2x= -8/4

x=-1/4 or x=-1