General Forms of a Sequence

A sequence is an ordered list of numbers and the sum of the terms of a sequence is a series

General Form of an Arithmetic Sequence

a_n = a₁ +(n - 1)d

 In an arithmetic sequence, each term is equal to the previous term, plus (or minus) a constant. The constant is called the common difference (d).

General Form of an Geometric Sequence

a_n = a₁·r^n-1

In a geometric sequence, each term is equal to the previous term, multiplied (or divided by) a constant. The constant is called the common ratio.To find the common ratio, divide the second term by the first term