How do I factor out the greatest common monomial factor?

1) 9m^7 - 3m^2

2) 12a^5 + 8a

3) I need to describe and correct the error in facotring out the greatest common monomial factor of 18x^8 - 9x^4 - 6x^3

18x^8 - 9x^4 - 6x^3 = 3x(6x^7 - 3x^3 - 2x^2) is INCORRECT

1 answer

1. 3m^2(3m^5-1).

2. 4a(3a^4+2).

3. 18 = 3*3*2.
9 = 3*3.
6 = 3*2.
GCF = 3x^2.

Note: The lowest power of x was used.