9﹙x+y﹚²-4﹙x-y﹚²

问题描述:

9﹙x+y﹚²-4﹙x-y﹚²

9﹙x+y﹚²-4﹙x-y﹚²
=【3﹙x+y﹚】²-【2﹙x-y﹚】²
=【3(x+y)+2(x-y)】【3(x+y)-2(x-y)】
=(3x+3y+2x-2y)(3x+3y-2x+2y)
=(5x+y)(x+5y)