=a^2(a+3)-9(a+3)=(a^2-9)(a+3)=(a-3)(a+3)(a+3)=(a-3)(a+3)^2
a^3+3a^2-9a-27=(a^3+3a^2)-(9a+27)=(a^2-9)(a+3)=(a+3)^2 * (a-3)
=(a+3)^2 * (a-3)