1、
=(4a²b^4)(3a²b-2ab-1)
=12a^4b^5-8a³b^5+4a²b^4
2、
=4(a²-2ab+b²)-(2a+b)(2a-b)
=4a²-8ab+4b²-4a²+b²
=-8ab+5b²
3、
=[x-(y-1)][x+(y-1)]
=x²-(y-1)²
=x²-y²+2y-1
4、
=(x+3y)(x-3y)(x²+9y²)
=(x²-9y²)(x²+9y²)
=x^4-81y^4