To find the sum S∞ of an infinite series when –1 < r < 1:SEQUENCES
Our final commonly seen miscellaneous topic is typified by Example 12. It’s a topic that entails a lot
of formulas.
Example 12This one’s a snap if you know the formula. To find the nth term of a geometric sequence, you need
to know the first term (here given as 3), and you need to know the ratio r between consecutive
terms. You’re not given consecutive terms but rather the first and the third. The second term would
be the first term times r, and the third term would be the second term times r. Therefore,
1. If the first term in a geometric sequence is 3, and if the third term is 48, what is the 11th term?(A) 228(B) 528(C) 110,592(D) 3,145,728(E) 12,582,912