Question

(x+y+z)+(x-y-z)-(x-y+z)先去括号，再合并同类项

要快啦，急死了。。。。。。。

Answer 1

(x+y+z)+(x-y-z)-(x-y+z)
=x+y+z+x-y-z-x+y-z
=x+y-z