(x+y+z)+(x-y-z)-(x-y+z)先去括号,再合并同类项急死了.
问题描述:
(x+y+z)+(x-y-z)-(x-y+z)先去括号,再合并同类项
急死了.
答
(x+y+z)+(x-y-z)-(x-y+z)
=x+y+z+x-y-z-x+y-z
=x+y-z