Determine whether the geometric series is convergent or divergent. If it is convergent, find its sum. 9 - 11 + 121/9 - 1331/81 + ...
Step 1
To see 9 - 11 + 121/9 - 1331/81 + ... as a geometric series, we must express it as sum from n=1 to infinity of ar^(n-1).
For any two successive terms in the geometric series, the ratio of the two terms, ar^n / ar^(n-1), simplifies into an algebraic expression given by r.
Step 2
In our series 9 - 11 + 121/9 - 1331/81 + ..., the ratio (-1331/81) / (121/9) is r = -11/9.
Step 3
In the series 9 - 11 + 121/9 - 1331/81 + ..., the n = 3 term is 121/9.
If this is to equal ar^2 = a(-11/9)^2, then a = 9.
Step 4
Similarly, -1331/81 = ____ (-11/9)^3.
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