Question

The sum to infinity of a geometric sequence is 27/2 while the sum of first three terms is 13. Find the sum of the first five terms.​

Answer 1

Step-by-step explanation:

If a sequence is geometric there are ways to find the sum of the first n terms, denoted Sn, without actually adding all of the terms.

To find the sum of the first Sn terms of a geometric sequence use the formula

Sn=a1(1−rn)1−r,r≠1,

where n is the number of terms, a1 is the first term and r is the common ratio.

The sum of the first n terms of a geometric sequence is called geometric series.