9(x+2y)^2-4(x-2Y)^2

问题描述:

9(x+2y)^2-4(x-2Y)^2

9(x+2y)^2-4(x-2Y)^2
=[3(x+2y)]^2-[2(x-2Y)]^2
=[3(x+2y)+2(x-2Y)][3(x+2y)-2(x-2Y)]
=(5x+2y)(x+10y)