先去括号,再合并同类项：2(2n-3m)-(2m- - 知识问答

先去括号,再合并同类项：2(2n-3m)-(2m-3n)还有(x-2y+1)-3(2x-y-2)

4个回答

2(2n-3m)-(2m-3n)
=4n-6m-2m+3n
=7n-8m
(x-2y+1)-3(2x-y-2)
=x-2y+1-6x+3y+6
=-5x+y+7
已知a-b=3,c+d=2,
(b+c)-(a-d)
=b+c-a+d
=-(a-b)+c+d
=-3+2
=-1

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