x^2-4x+5=8 so let's complete the square, subtract 5 from both sides
x^2-4x=3 halve the linear coefficient, square it, and add it to both sides...(-4/2)^2=4
x^2-4x+4=7 now the left side is a perfect square of the form
(x-2)^2=7 take the square root of both sides
x-2=±√7 add 2 to both sides
x=2±√7
So A. is your answer.
