3a^3b-12ab^3+9a^4b^2-36a^2b^4
=3a²b(a²-4b²)+9a²b²(a²-4b²)
=(a²-4b²)(3a²b+9a²b²)
=(a+2b)(a-2b)(3a²b)(1+3b)
=3a²b(a+2b)(a-2b)(3b+1)第二项是a，不是a²。3a^3b-12ab^3+9a^4b^2-36a^2b^4=3ab(a²-4b²)+9a²b²(a²-4b²)=(a²-4b²)(3ab+9a²b²)=(a+2b)(a-2b)(3ab)(1+3ab)=3ab(a+2b)(a-2b)(3ab+1)