因式分解:9x2-y2-4y-4=_.
问题描述:
因式分解:9x2-y2-4y-4=______.
答
9x2-y2-4y-4,
=9x2-(y2+4y+4),
=9x2-(y+2)2,
=(3x+y+2)(3x-y-2).