Explanation:
Since you are solving for two numbers that multiply into 56 and since we know they are both integers then they have to be an integral multiple of 56 which are 1,2,4,7,8,14,28, and 56. There are also negative values for every single value listed.
I will restate the example products
so 1 would be paired with 56 to get a product of 56
and -1 with -56 would be a product of 56
2 with 28 to get 56
-2 with -28 to 56
4 with 14 to get 56
-4 with -14 to get 56
7 with 8 to get 56
-7 with -8 to get 56
Hope this helps :)