How do you find the sum of #1+1/5+1/7^2+1/7^3+1/7^9+...+1/7^n+...#?
The question is not very clear...in answering I assume that for
We can write the sum as:
Focus on the series: clearly we have:
Thus at the second member we have the sum of a geometric series and the partial sum of a geometric series of ratio