Arithmetic progression is a (n)-a (n- 1) = d D, and if d is a constant, then q=a(n)/a(n- 1).
Generally speaking, if a series starts from the second term, and the difference between each term and its previous term is equal to the same constant, this series is called arithmetic progression.
Generally speaking, if a series starts from the second term and the ratio of each term to its previous term is equal to the same constant, this series is called geometric series.