Yes, find the prime factors.
4 can be written as 2*2.
g^4 can be written as g*g*g*g.
That is the prime factorization of the first expression.
4g^4 can be written as 2*2*g*g*g*g.
34 can be written as 2*17.
And again we can split up the g business: g^3 is g*g*g.
34g^3 can be written as 2*17*g*g*g.
What do these expressions have in common?
They have a 2 in common,
and three of the g's in common, ya?
Therefore the GCF(4g^4, 34g^3) = 2g^3.