计算:(x-y+z)(-x+y+z)

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计算:(x-y+z)(-x+y+z)
计算:(x-y+z)(-x+y+z)

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

原式=[z+(x-y)][z-(x-y)]
=z² -(x-y)²
=z²-x²-y²+2xy

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

这是一个化简题
先把负号提出来
原式可以化为
[z+(x-y)][z-(x-y)]
然后展开
z^2-(x-y)^2
最后
z^2-x^2+2xy-y^2
明白了吗?