Объяснение:

1) ab-ac+b³-b²c-7c+7b=(ab-ac)+(b³-b²c)-(7c-7b)= a(b-c)+(b³-b²-c)-7(c-b)= (a-7)(b-c)(b³b²-c)

2) (x-y)(x+y-3)

3) (x+y)(2-a)

4) (a-b)(b-3)