(-2x+2)-(-2x+2)为什么等于-2(x1-x2)

问题描述:

(-2x+2)-(-2x+2)为什么等于-2(x1-x2)

应该是(-2x1+2)-(-2x2+2)
=-2x1+2+2x2-2
=-2x1+2x2
=-2(x1-x2)