6a^2b-9ab^2+3ab a^3-6a^2-7a （x^2+x)^2-(x+1)^2

6a^2b-9ab^3+3ab
=3ab(2a-3b^2+1)
a^3-6a^2-7a
=a(a^2-6a-7)
=a(a+1)(a-7)
(x^2+x)^2-(x+1)^2
=(x^2+x+x+1)(x^2+x-x-1)
=(x^2+2x+1)(x^2-1)
=(x+1)^2(x+1)(x-1)
=(x+1)^3(x-1)