Arithmetic Series Sum Formula Quizmaster
Review the Lesson | MATHguide homepage Updated June 18th, 2023

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Use the first 21 terms of the following arithmetic series for the problem below:

-5 - 3 - 1 + 1 + ...


What is the 21th term?		 a21 =
What is the sum of the first 21 terms? S21 =