9(2x-y)²-16(x+2y)²
原式=[3（2x-y）]²-[4(x+2y)]²
=[3（2x-y)+4(x+2y)][3(2x-y)-4(x+2y)]
= (6x-3y+4x+8y) (6x-3y-4x-8y)
=(10x+5y)(2x-11y)
=5(2x+y)(2x-11y)