Select the factors of xy − 4x + 2y − 8.
a. (x − 2)(y + 4)
b. (x + 2)(y − 4)
c. (x − 4)(y + 2)
d. (x + 4)(y − 2)

We need to factor by grouping. Group xy with -4x and 2y with -8 and factor each group.

(xy-4x)+(2y-8)
x(y-4)+2(y-4)
b. (x+2)(y-4)

Hope that helps.

First what you must do is see if there is a greatest common factor. As you will see in this particular problem, there is not, so therefore you must factor by grouping.

(x+2)(y-4) is definitely the correct answer because if you really think about it,     x*y=xy, x*-4=-4x, 2*y=2y, and 2*-4=-8!

So, I definitely believe that the answer is unmistakably (x+2)(y-4)!