计算:(x－2y+z)(-x+2y+z)要过程,谢

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计算:(x－2y+z)(-x+2y+z)要过程,谢
计算:(x－2y+z)(-x+2y+z)要过程,谢

计算:(x－2y+z)(-x+2y+z)要过程,谢
(x－2y+z)(-x+2y+z)
＝〔z+(x-2y)][z-(x-2y]
=z^2-(x-2y)^2
=z^2-(x^2-4xy+4y^2)
=z^2-x^2+4xy-4y^2

（x－2y+z)(-x+2y+z)
=（z+x-2y）【z-（x-2y）]
=z²-（x-2y）²
=z²-x²-4y²+4xy

原式=[z+（x-2y）][z-(x-2y)]
=z²-（x-2y）²
=z²-x²-4y²+4xy

原式=-(x-2y+z)(x-2y-z)
=-[(x-2y)+z][(x-2y)-z]
=-[(x-2y)²-z²]
=-(x-2y)²+z²
=-(x²-4xy+4y²)+z²
=-x²+4xy-4y²+z²

(x－2y+z)(-x+2y+z)=[z+（x-2y)][z－(x-2y)]=z²-(x-2y）²=z²-x²-4y²+4xy

原式=-(x-2y+z)(x-2y-z)
=-[(x-2y)+z][(x-2y)-z]
=-[(x-2y)²-z²]
=-(x-2y)²+z²
=-(x²-4xy+4y²)+z²
=-x²+4xy-4y²+z²

:(x－2y+z)(-x+2y+z)=[z+(x-2y)][z-(x-2y)]=z²-（x-2y)²=z²-x²+4xy-4y²

1.提负号：=-（x-2y+z)(x-2y-z)
2.把x-2y看做一个整体：=-[（x-2y)^2-z^2]................^2就是平方的意思啦~
3.平方差运算：=-（x^2-4xy+4y^2-z^2）=-x^2+z^2-4y^2+4xy

-x^2+2xy+zx+2xy-4y^2-2yz-zx+2yz+z^2=-x^2-4y^2+z^2+4xy

=-X二-2XY+XZ+2XY-4Y二-2YZ-XZ+2YZ+Z二=Z二-X二-4Y二
备注：平方写不出来，就由二代替

由公式（x+y）(x-y)=x²-y²可得
（x－2y+z)(-x+2y+z)
=（z+x-2y）[z-（x-2y）]
=z²-（x-2y）²
看题目的具体要求，有时下面也可以不必再化开了，本来就是为了化繁为简，在把（x-2y）²化开就又变为化简为繁了

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