合并同类项1.
1.-t-t-t 2.9ab-4ab-ab-7ab+5ab 3.-12x+6y-3+10x-2-y 4.5m-7n-8p+5n-9m-p
1.-t-t-t=(-1-1-1)=-3t 2.9ab-4ab-ab-7ab+5ab=(9-4-1-7+5)ab=2ab 3.-12x+6y-3+10x-2-y=(-12+10)x+(6-1)y-2=-2x+5y-2 4.5m-7n-8p+5n-9m-p=(5-9)m+(5-7)n-(8+1)p=-4m-2n-9p