Answer
See below.
Work Step by Step
An arithmetic sequence is defined as an array of numbers in which each term excluding the initial term will be the result of adding the same number to the proceeding term . This number is known as the common difference between every two consecutive terms.
This number is denoted as $d$.
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 $a_n=a_1+(n-1) d$
