Oh wait I think I understand
When you use foil to expand, you multiply the variables together, then the sum of the products of the inside and outside terms, and the constants. Example: (x+2)(x-3)=x^2-x-6.
Because of this, we need to factorize 2008, so for the middle term we get x+2008x=2009x, 2x+1004x=1006x, 4x+502x=506x, 8x+251x=259x, and we take the smallest coefficient and that's our answer