1 2x-(x+3y)-(-x-y)-(x-y)＝
2 -2(3x+z)-(-6x)+(-5y+3z)=
3 9a2+[7a2-2a-(-a2+3a)]=
4 -(7x-y-2z)-｛[4x-(x-y-z)-3x+z]-x｝=
5 2x2-｛-3x-[4x2-(3x2-x)+(x-x2)]｝=
6 5m2n+(-2m2n)+2mn2-(+m2n) =
7 (4xy2-2x2y)-( )=x3-2x2y+4xy2+y3=
8 2x+2y-[3x-2(x-y)]=
9 2y+(-2y+5)-(3y+2)＝
10 2a-(3a-2b+2)+(3a-4b-1)=
这几道题目应该蛮省力的,你自己算算吧