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.
