Solve by completing the square: x^2+15=8x

x^2+15=8x

x^2-8x=-15

x^2 - 2 (x) (4) = - 15

adding 16 on both sides

x^2 - 2 (x) (4) + 16=-15+16

x^2 - 2 (x) (4) + 4^2 = 1

(x-4) ^2=1

taking square root on bothsides x-4 = + - 1

so x-4=1 or x-4=-1

x-5 or x=3