1) 2ab-a=a (2b-1)

2) 25ax+50a^2=25a (x+2a)

3) m^10 - m^9= m^9 (m-1)

4) a (3b+c)-x (3b+c)=(3b+c)(a-x)

5) 2p (a-x)-(x-a)=2p(a-x)+(a-x)=(a-x)(2p+1)

6) 3 (a-2)^2 -3 (2-a)=(a-2)(3 (a-2)-3)=(a-2)(3a-6-3)=(a-2)(3a-9)