Solve x^2 — 8x + 15 = 0 by completing the square.
The solutions are x =
and x=

X^2-8x+15=0
Completing the square
Therefore x^2 -8x + (8/2)^2 -(8/2)^2+15=0
(X-4)^2 -16+15
(x-4)^2 -1=0
(x-4)^2=1
x-4=+1,-1
x=5 and x=3

If you make it a little more clear i can answer it