# How do you find the 10-th partial sum of the infinite series #sum_(n=1)^oo(0.6)^(n-1)# ?

##### 1 Answer

Hi, thanks for asking.

You have a geometric series here with common ratio r = 0.6, and the partial sum

You want the first ten terms...

If you calculate the power exactly you get

The general formula

is also useful but we did better; we derived it from scratch!

As an extra brain rep, see if you can verify this formula using our subtraction method, and then maybe figure out the infinite sum.

\dansmath - made from scratch, every time./