因式分解9（x-y）²+12（x²-y²）+4（x+y）²
问题描述：
因式分解9（x-y）²+12（x²-y²）+4（x+y）²
答
原式=[3(x-y)]²+12(x+y)(x-y)+[2(x+y)]²
=[3(x-y)+2(x+y)]²
=(5x-y)²