To get the Greatest Common Factor, we can start by getting all prime factor of both. The "n" in the expressions can be left in this way, so et's focus on the numbers 39 and 48.
39 can be divided by 3 to get 13. Both are already primes, so we can write:
48 can be divided by 2 to get 24, again to get 12, again to get 6 and once more to get 3, which is prime. We divided 48 by 2 four times, so we can write:
Now we compare the factor and get the ones that are common to both. Both have a single 3. Also, boths have "n" twice (39n^3 has three times, but 48n^2 has only twice, so we stick to it).
So, the common factors are:
