a+(b+c)=?a-(b+c)=?a+(b-c)=?a-(b-c)=?(8x-5x0-(4x-9y)=?(2x+2y)+(-5x+2y)=?

问题描述:

a+(b+c)=?a-(b+c)=?a+(b-c)=?a-(b-c)=?(8x-5x0-(4x-9y)=?(2x+2y)+(-5x+2y)=?

a+b+c a-b-c a+b-c a-b+c
8x-5x-(4x-9y)= -x+9y
(2x+2y)+(-5x+2y)= -3x+4y