Answer:
x = 4±sqrt(19)
Explanation:
Assuming you meant x^2 -8x = 3
Take the coefficient of x
-8
Divide by 2
-8/2 =-4
Square it
(-4)^2 = 16
Add this to each side
x^2 -8x +16= 3+16
The number inside the square term is the coefficient divided by 2
(x-4)^2=19
Take the square root of each side
sqrt((x-4)^2=±sqrt(19)
x-4 = ±sqrt(19)
Add 4 to each side
x-4+4 = 4±sqrt(19)
x = 4±sqrt(19)