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问题: 合并同类项

m-2(3-2n)
a-{b+(c-d)}
-(5x+y)-3X(2x-3y)
x-2(4x-2m)
2a+(x-y)-2(a+b)-(x+y)

解答:

m-2(3-2n) =m-(6-4n)=m+4n-6
a-{b+(c-d)}=a-〔b+c-d〕=a-b-c+d
-(5x+y)-3X(2x-3y)=-5x-y-6x2+9xy
x-2(4x-2m) =x-8x+4m=-7x+4m
2a+(x-y)-2(a+b)-(x+y)=2a+x-y-2a-2b-x-y=-2y-2b
字母相同的合并在一起