help with binomials?

Question

Sums and differences of cubes??

Factor Completly:

1) 3z^5 - 3z^2

2) a^9 + b^12 c^15

Answer 1

1) 3z^5 - 3z^2
=3z^2 (z^3 - 1)
=3z^2 (z - 1)(z^2 + z + 1)
= 3z^2 (z - 1)(z +1/2 + sqrt(3)i/2)(z +1/2 - sqrt(3)i/2)

2) a^9 + b^12 c^15
= (a^3)^3 + (b^4c^5)^3
= (a^3 + b^4c^5)[(a^3)^2 - a^3b^4c^5 + (b^4c^5)^2]