5mn-7mn+3m-m=(5-7)mn+(3-1)m=-2mn+2m=2m(1-n)
mn-3mnk+4mn=mn(1-3n+4)=mn(5-3n)
2ab-ab+5ab=ab(2-1+5)=6ab
7ab-5abc-2ab=2ab(5-3c-1)=2ab(4-3c)
5mn-7mn+3m-m=(5-7)mn+(3-1)m=-2mn+2m=2m(1-n)
mn-3mnk+4mn=mn(1-3n+4)=mn(5-3n)
2ab-ab+5ab=ab(2-1+5)=6ab
7ab-5abc-2ab=2ab(5-3c-1)=2ab(4-3c)