-{+【-(x+y)】}+{-【-(x+y)】}去括号等于

问题描述:

-{+【-(x+y)】}+{-【-(x+y)】}去括号等于

-{+【-(x+y)】}+{-【-(x+y)】}
=-【-(x+y)】-【-(x+y)】
=(x+y)+(x+y)
=x+y+x+y
=2x+2y