感觉是你写错了,应该是下面的这个吧
(x+y-z)²-(x-y+z)²
=[(x+y-z)-(x-y+z)][(x+y-z)+(x-y+z)]
=(x+y-z-x+y-z)(x+y-z+x-y+z)
=(2y-2z)2x
=4xy-4xz
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