Need help on this math problem!

Complete the square in the equation below:

x^2 + 8x = 4

x²+8x=4

x²+8x+16=4+16

(x+4)²=20

x=...-b (+/-)squareroot of:(b^2-4ac)..............
..... _________________________.........
.........................2a ...............................

x^2 + 8x - 4 = 0
a=1 b=8 c=-4

using the formular for (+) : x = -4 + 2(root5) or 0.472
using the formula for (-) : x = -4 - 2(root5) or -8.472

(x - 0.472)(x + 8.472) = 0 (3decimalplaces)

id double check it yourself though to be sure