因式分解:-4(x-2y)2+9(x+y)2.
问题描述:
因式分解:-4(x-2y)2+9(x+y)2.
答
-4(x-2y)2+9(x+y)2,
=[3(x+y)]2-[2(x-2y)]2,
=(3x+3y+2x-4y)(3x+3y-2x+4y),
=(5x-y)(x+7y).