Answer:
7a^4b^3
Explanation/Steps to solve:
First you separate 49 and 21 from the variables. Then you find their GCF.
The GCF of 49 is 21 is 7.
Then you find the GCF of the variables.
a^4b^3 and a^4b^5
how many As and Bs do they have in common?
both variables have 4 As and both have 3 Bs. It can't be 5 Bs since the other variable only has 3. 3 is less than 5 which means that there can be a 3 in the other variable (b^5).
So we rewrite how much As and Bs they have.
4 As = a^4
3 Bs = b^3
---> a^4b^3
then we combine both the GCF of the numbers and the variables,
7a^4b^3