The form (x - p)^2 = q is the form that completing the square will leave us with.
---Add 5 to both sides
x^2 - 8x = 5
---Divide the b term by 2, and square it. Then, add that number to both sides.
-8/2 = -4
(-4)^2 = 16
x^2 - 8x + 16 = 5 + 16
x^2 - 8x + 16 = 21
---Factor!
(x - 4)^2 = 21
p = 4
q = 21
Hope this helps!! :)
