The factor pairs of 20 are (20,1)(10,2)(5,4)
Even considering their negative counterparts, none of them add up to -8
If that was -20, you could use -10 and 2.
-10 and 2 make -8 and multiply to -20
20
-12
12
20
2584
-28
580
20
26
-70
9 and 11.
2 and 10