Sum It Up

An arithmetic sequence can be written in sequence notation using the function an = a1 + d(n − 1).

A geometric sequence can be written in sequence notation using the function an = a1 • rn−1.

A geometric series is a sum of a list of numbers with a common ratio. The sum of a series is determined by the function Sn =

a1(rn)−a1/r-1

Sigma notation can be used to find the sum of a sequence with a given number of terms. The Greek symbol Σ can be used with a lower index and upper index to indicate which terms of the sequence to add together.

Focus Questions

To achieve mastery of this lesson, make sure you develop responses to the following questions:

How can you write arithmetic and geometric sequences with formulas using sequence notation?

How can you use the formula for the sum of a finite geometric series to solve problems?

How is sigma notation used to evaluate a series?