use square root method to solve
6z^{2} + 4 = 220
6z^{2} = 220 - 4
6z^{2} = 216
z^{2} = 216/6
z^{2} = 36
z = ± √36 ---> z = ±6
use square root method to solve
6z^{2} + 4 = 220
6z^{2} = 220 - 4
6z^{2} = 216
z^{2} = 216/6
z^{2} = 36
z = ± √36 ---> z = ±6