take 1/2 of the linear coefient (-8) and square it
-8/2=-4, (-4)^2==16
add that to both sides
x²-8x+16+12=16
complete the square
(x-4)²+12=16
minus 12 both sides
(x-4)²=4
sqrt both sides, remember positive and negative roots
x-4=+/-2
add 4
x=4+/-2
x=4+2 or 4-2
x=6 or 2
(2,6)
A is answer
