# Activities

• • • ##### Subject Area

• Math: Algebra II: Sequences

• ##### Author 9-12

60 Minutes

• ##### Device
• TI-Nspire™ Navigator™
• TI-Nspire™
• TI-Nspire™ CAS
• ##### Software

TI-Nspire™
TI-Nspire™ CAS

2.0

## Sums of Sequences #### Activity Overview

In this activity, students will develop formulas for the sum of arithmetic and geometric sequences. Students will then find the sum of sequences using the formulas developed.

#### Key Steps

• In this activity, students will first perform a numerical process/proof to find the sum of an arithmetic sequence. To do this, they will be entering the sequence in reverse order and finding the sums of the rows.

• After students develop a formula for the sum of an arithmetic sequence, they will apply the formula.

• In the second part of the activity, students develop the formula for the sum of a geometric sequence. To do this, they will multiply each term in the sequence by the common ratio, find the difference between the two different values, and divide by a value to determine the sum of column A.