计算:(x－2y+z)(-x+2y+z)要过程,谢
问题描述：
计算:(x－2y+z)(-x+2y+z)要过程,谢
答
(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