if the ratio of each term in a sequence starting from the 2nd term to its previous term is equal to the same constant, the sequence is called a geometric sequence. this constant is called the common ratio of the geometric sequence. the common ratio is usually represented by the letter q (q≠0), and the geometric sequence a1≠0. note: when q=1, an is a constant column.

general formula:a_n = [a₁ q ^(n-1)]

a₁ - first item

n - number of terms

q - common ratio