(x-2y+z)(-x+2y+z).
问题描述:
(x-2y+z)(-x+2y+z).
答
(x-2y+z)(-x+2y+z),
=[z+(x-2y)][z-(x-2y)],
=z2-(x-2y)2,
=z2-(x2-4xy+4y2),
=z2-x2+4xy-4y2.