化简x-y+2(x-y)-4(x-y)得 A -x-y B -x+y C x-y D x+y

问题描述:

化简x-y+2(x-y)-4(x-y)得 A -x-y B -x+y C x-y D x+y

x-y+2(x-y)-4(x-y)
=x-y+2x-2y-4x+4y
=-x+y
选B