#### Answer

See below.

#### Work Step by Step

An arithmetic sequence is defined as an array of numbers which consists of a common difference between every two consecutive terms.
For example: $1, 3,5, 7,....$
Here, the common difference is $d=3-1=2$
The sum of an arithmetic sequence is given by: $S_n=\dfrac{n}{2}[a_1+a_n]$ and the nth term for an arithmetic sequence is given by $a_n=a_1+(n-1) d$