Calculate the sum of the series whose partial sums are given.

When we calculate the sum of the series C∞, n=1 ∑ an

whose partial sums are given

sn = 2 - 9 (0.9) ⁿ

We can get an answer which is 2.

It has an infinite number of terms, the infinite series. The partial sum is the sum of the first n terms, Sn. The answer in this question is 2.