Question

(x+y+z)(-x+y+z)(x-y+z)(x+y-z)等于什么?

Answer 1

题目应为:

（x+y-z)(x-y+z)-(x+y+z)(x-y-z)

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

=x^2-(y-z)^2-[x^2-(y+z)^2]

=(y+z)^2-(y-z)^2

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

=2y*2z

=4yz