Question

What is the sum of an 8-term geometric sequence if the first term is 10 and the last term is
781,250?

Answer 1

@e.mccormick

Answer 2

So ypu have \(ar^n\) as the normal thing for any term. When n=0, you are at the first term so it becomes \(ar^0=a\). this means you know a=10. ou also know that \(781250=10r^7\) so you can use that to find r. Once you have r, you can do the sum.