Explanation:
Simple
8x4 + 8x3 + 27x + 27
First there is 8 common on one side and 27 on another
So
8x3 ( x + 1) + 27 ( x + 1)
(8x3 + 27) and (x + 1) are the factors
3 2x3 - 32x2 + 120x - 1920
2x2 ( x - 16) + 120 (x - 16)
(x - 16) and ( 2x2 + 120) are the factors
Hope you have understood and will do the second one