This is an arithmetic sequence since there is a common difference between each term. In this case, adding 5 5 to the previous term in the sequence gives the next term. In other words, an = a1 +d(n−1) a n = a 1 + d ( n - 1). This is the formula of an arithmetic sequence. Substitute in the values of a1 = 7 a 1 = 7 and d = 5 d = 5.
