Answer:
GCF: 2d²
Explanation:
Write out all the factors of 6:
6
-----------
6 1
3 2
Write all the factors of 10:
10
--------------
10 1
5 2
The GFC of both of those numbers is 2.
Since both numbers have a variable of d, and since they both have exponents, you can multiply both numbers by d², because there is at least one d² in each variable.
Your full answer would be: 2d²(3d³ - 5)
If you use foil, remember you don't multiply exponents, you add them.