(x+y-z)(x-y+z)-(x+y-z)(x-y-z)要过程
1个回答

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

=x²-(y-z)²-(x-z)²+y²

=x²-y²+2yz-z²-x²+2xz-z²+y²

=2yz+2xz-2z²

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