4.
1) ......=2+a+6+3a=4a+8=4(a+2)
2) .....=3-a+6-2a=9-3a=3(3-a)
3) ....=m-n-5m+5n=4n-4m=4(n-m)
4) ....=x-y-4x+4y=3y-3x=3(x-y)
5) .....=(4b+1)(a+b)
6) ....=(5x+1)(x+y)
7) ....=(a-1)(x-y)
8) ....=(c+1)(m-n)
5.
1) ....=a-b+2(a-b)=(a-b)(1+2)=3(a-b)
2) ....=c-d+3(c-d)=(c-d)(1+3)=4(c-d)
3) ....=2(a-b)-c(a-b)=(a-b)(2-c)
4) ....=3(c-d)-a(c-d)=(c-d)(3-a)
5) ....=2(a-b)+c(a-b)=(a-b)(2+c)
6) ....=3(c-d)+a(c-d)=(c-d)(3+a)