400-800 = -400
800 = 1 x 800800 = 2 x 400800 = 4 x 200800 = 5 x 160800 = 8 x 100800 = 10 x 80800 = 16 x 50800 = 20 x 40800 = 25 x 32
There are 9 factor pairs of 800.800 = 1 x 800800 = 2 x 400800 = 4 x 200800 = 5 x 160800 = 8 x 100800 = 10 x 80800 = 16 x 50800 = 20 x 40800 = 25 x 32