First find common factor for parameters. I mean to find common factor number 9,15,12
first, write the divisors:
Divisors of 9: 1,3,9
divisors of 12: 1,2,3,4,6,12
divisors of 15: 1,2,3,5,15
so see, that GCF of 9,12,15 is 3.
Now, count GCF of x^2, x^4, x^6
GCF 2,4,6 is 2, so the result is x^2
and know finally GCF these terms is [tex]3x^{2}[/tex]