# Is this formula for a arithmetic sequence? #sum_(k=0)^(k=n-1)ar^k=a((1-r^n)/(1-r))#

##### 1 Answer

Aug 13, 2016

The formula is for sum of a geometric sequence and not arithmetic sequence. See details below.

#### Explanation:

This formula is not about arithmetic sequence, but is for a geometric sequence.

Note that sequence starts from

Then changing

The right hand side gives the value of sum of the sequence for