![S_n=\frac{n}{2}[2a+(n-1)d]](/tpl/images/0428/4943/b603c.png)
![S_{21}=\frac{21}{2}[2(-5)+(21-1)(2)]](/tpl/images/0428/4943/b8082.png)
![S_{21}=\frac{21}{2}[-10+40]](/tpl/images/0428/4943/b73b6.png)
What is the sum of the first 21 terms of this arithmetic series?
-5+(-3)+(-1)+1+...
Mathematics, 21.12.2019 01:31 jfrjtwrg
What is the sum of the first 21 terms of this arithmetic series?
-5+(-3)+(-1)+1+
Answers: 2
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