1、(x²-x-6)(x²-x-12)
=(x²-x)²-18（x²-x)+81-81+72
=(x²-x-9)²-9
=[(x²-x-9)+3][(x²-x-9)-3]
=(x²-x-6)(x²-x-12)
2、(2x-4y-4)(2x-4y-8)或(4y-2x-4)(4y-2x-8)
=(2x-4y)²-12(2x-4y)+36-36+32
=(2x-4y-6)²-4
=[(2x-4y-6)+2][(2x-4y-6)-2]
=(2x-4y-4)(2x-4y-8)