### Home > A2C > Chapter 12 > Lesson 12.1.2 > Problem 12-35

12-35.

Consider the series 21 + 17 + 13 + … + −99 as you answer the questions in parts (a) through (c) below. Homework Help ✎

Write an expression for the

*n*^{th}term.How many terms are in the series? How can you tell?

What is the sum of this series?

Use a system of equations or look at the difference between terms and the value of the first term.

Set the equation you found in part (a) equal to −99 and solve for *n*.

Use the rectangle method or Antonio's method.

−1209