Which of the following is a factor of 2xy + 8y - 8x - 32?

5

x + 4

x2 - 4x + 16

All of the above

You could start by eliminating wrong answer (s):

(a) 5 is definitely not a factor of the given 2xy + 8y - 8x - 32,

(d) x^2 - 4x + 16 (not x2 - 4x + 16) is not a factor (it has no y terms)

On the other hand:

(b) 2 definitely divides evenly into 2xy + 8y - 8x - 32: 2 (xy + 4y - 4x - 16)

(c) x + 4 divides evenly into both xy + 4y and - (4x + 16):

We get 2 (x + 4) [y - 4]