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

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(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+y-z)(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-(y-z)]-(x+y+z)[x-(y+z)]
=[x²-(y-z)²]-[x²-(y+z)²]
=x²-(y-z)²-x²+(y+z)²
=(y+z)²-(y-z)²
=(y+z+y-z)(y+z-y+z)
=2y2z
=4yz

[x+(y-z)][x-(y-z)]-[x+(y+z)][x-(y+z)]
=[x^2-(y-z)^2]- [x^2-(y+z)^2]
下面自己可以做。