Explanation:
x²+4x=8
rearrange
x² + 4x - 8 = 0
half of 4 is 2
so
x² + 4x + 2² - 2² - 8 = 0
do x² + 4x + 2²
multiplies to give 4 adds to give 4
2+ 2
(x + 2)²
(x + 2)² - 2² - 8
(x + 2)² - 4 - 8
(x + 2)² - 12
(x + 2 + √12) (x + 2 - √12)
√12 = √4 * √3 = 2 √3
(x + 2 + 2√3) (x + 2 - 2√3)