Solve x^2+8x-5=0 using completing the square

by completing the square we write the equation as (x+b/2)^2-b/2^2+c, in this case b=8 (the coefficient of x) and c=5 so we have (x+4)^2-16-5=0, which equals (x+4)^2-21=0. Now by rearranging we get (x+4)^2=21, which goes to x+4=+or-sqrt(21). Therefore x=sgrt21 -4 or x=-sqrt21 -4