what is a geometric sequence
Geometric sequences and series. A geometric sequence is a sequence of numbers that follows a pattern were the next term is found by multiplying by a constant called the common ratio, r. Example. Write the first five terms of a geometric sequence in which a 1 =2 and r=3. We use the first given formula: Just as with arithmetic series it is possible to find the sum of a geometric series. It is found by using one of the following formulas: Videolesson: use the formula for the sum of a geometric series to determine the sum when a 1 =4 and r=2 and we have 12 terms. 1  Pre-Algebra. 2  Algebra 1. 3  Algebra 2. 4  Geometry.