几道初一合并同类项的题.各位高手,帮帮忙吧!

几道初一合并同类项的题.各位高手,帮帮忙吧!
-0.8a²b-6ab-1.2a²b+5ab+a²b
2/3a²-1/2ab+3/4a²+ab-b²
6x²y+2xy-3x²y²-7x-5yx-4y²x²-6x²y
4x²y-8xy²+7-4x²y+12xy²-4
3xm+3-9xm+2+5xm+1+7xm+2-10xm+3-5xm+1(m+1 m+2 m+3为字母指数）
2(x-3y)²-3(x-3y)³-(3y-x)²-(3y-x)³
尽量快点,我会追加分的,最好有过程!谢谢了^_^

-0.8a²b-6ab-1.2a²b+5ab+a²b=-a²b-ab
2/3a²-1/2ab+3/4a²+ab-b²=17/12a²+1/2ab-b²
6x²y+2xy-3x²y²-7x-5yx-4y²x²-6x²y=-3xy-7x²y²-7x
4x²y-8xy²+7-4x²y+12xy²-4=4xy²+3
3x^(m+3)-9x^(m+2)+5x^(m+1)+7x^(m+2)-10x^(m+3)-5x^(m+1)=-7x^(m+3)-2x^(m+2)
2(x-3y)²-3(x-3y)³-(3y-x)²-(3y-x)³=2(x-3y)²-3(x-3y)³-(x-3y)²+(x-3y)³=(x-3y)²-2(x-3y)³

就是这个解释