（x-y+z)²-(x-y-z)²

题目

（x-y+z)²-(x-y-z)²

答案

（x-y+z)²-(x-y-z)²=（x-y+z+x-y-z）（x-y+z-x+y+z）=2（x+y）*2z=4（x+y）z