9(x+2y)²-25（x-2y)²=
问题描述：
9(x+2y)²-25（x-2y)²=
答
9(x+2y)^2-25(x-2y)^2
=[3(x+2y)+5(x-2y)][(3(x+2y)-5(x-2y)]
=(8x-4y)(-2x+16y)
=-8(2x-y)(x-8y)