Question 38234
this is much simpler than it looks, when you have x(a - b) + 2(a - b), for example, one sees the (a-b)'s are the same.  so you put them together!  now you have x+2 and (a-b), and that's your factoring answer.  (x+2)(a-b)
let's check jic!
xa-xb+2a-2b.  (i used the foil method)
ok so xa-xb both have n x and
2a-2b both have a 2 so
x(a-b)+2(a-b) is its factor, see, its right!  but now we have 2 a-b's we combine them and put the x+2 in ()'s.
(x+2)(a-b) ther4 A is the right answer.

another few examples, 
y(2a+c)-v(2a+c)=(y-v)(2a+c)
q(5q+3d)+c(5q+3d)=(q+c)(5q+3d)
get the pattern?