Algebra 2 / Trig
posted by Mathew .
Here is the problem that I'm having trouble with:
Rewrite each series in a sigma notation and find its sum.
1+.09+.81+...
I have no idea how I find the common difference or ratio in that one.

I don't think you will be able to do it with just those three terms.

perhaps you meant to type
1 + .09 + .0081 + ...
otherwise I agree with bob
If so, then
sum = [sigma] (.09)^(i1) , i goes from 1 to infinity.
use S(infinity) = a/(1r)