Answer
The sequence given by $a_{n} = ar^{n-1}$ is a geometric sequence in which a is the first term and r is the common difference. So for the geometric sequence $a_{n} = 2(5)^{n-1}$ the first term is 2 and the common difference is 5.
Work Step by Step
Formula for a geometric sequence; in this case a = 2 so it is the first term; r = 5 = the common difference
