1)18ab-15b^2=3b(6a-5b)
2)18a^3+6a^2=6a^2(3a+1)
3)a(a+3)-2(a+3)=(a+3)(a-2)
4)ax-ay+5x-5y=a(x-y)+5(x-y)=(x-y)(a+5)
5)x^2-xy-4x+4y=x(x-y)-4(x-y)=(x-y)(x-4)
7)x^2-49=(x-7)(x+7)
8)25x^2-10xy+y^2=(5x-y)^2=(5x-y)(5x-y)
9)4x^2y^2-9a^4=(2xy-3a^2)(2xy+3a^2)
10)25a^2-(a+3)^2=(5a+a+3)(5a-a-3)=(6a+3)(4a-3)
11)27m^3+n^3=(3m+n)(9m^2-3mn+n^2)