You can figure this out if you just look at (x+a)^2 = x^2 + 2ax + a^2. See, the constant term, a^2, is the coefficient of x (2a), divided by 2 (2a/2=a), and then squared (a^2)
<span>So you equation has 8x. 8/2 = 4, and 4^2 = 16. So the answer is A.</span>
