### Home > A2C > Chapter 12 > Lesson 12.3.1 > Problem 12-121

12-121.

Consider the series

How many terms are there?

Write an expression for the sequence, and find

when.

What is the sum?

Use the summation formula

12-121.

Consider the series

How many terms are there?

Write an expression for the sequence, and find

when.

What is the sum?

Use the summation formula