(1)(2x+y-5)(2x-y+5) (2)(x+y)(x-y)-(x-y)²

问题描述:

(1)(2x+y-5)(2x-y+5) (2)(x+y)(x-y)-(x-y)²

(1)(2x+y-5)(2x-y+5)=[2x+﹙y-5﹚][2x-﹙y-5﹚]=﹙2x﹚²-﹙y-5﹚²=4x²-y²+10y-25
(2)(x+y)(x-y)-(x-y)²=﹙x-y﹚﹙x+y-x+y﹚=2y﹙x-y﹚.