1、=3x^2(x^2-1)
=3x^2(x+1)(x-1)
2、=(x+2)(x-2)-(x-2)
=(x-2)(x+1)
3、=4ab
=4ab(3a+1)(x-y)
4、=(2x+5)(4x-3)
难输题,我没有输了,你应该看得懂.