SOLUTION: find the sum of the first n terms of the arithmetic series -10+(-5)+0+5+10 n=19

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Question 1108174: find the sum of the first n terms of the arithmetic series
-10+(-5)+0+5+10 n=19
Answer by ikleyn(52786) About Me  (Show Source):
You can put this solution on YOUR website!
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You have an arithmetic progression (AP) with the first term -10 and the common difference 5; the number of terms is 19.


For this data, the formula for the sum is 


S%5B19%5D = %28a%5B1%5D+%2B+%28d%2A%28n-1%29%29%2F2%29%2An = %28-10+%2B+%285%2A18%29%2F2%29%2A19 = 665.

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For introductory lessons on arithmetic progression, see the lessons
    - Arithmetic progressions
    - The proofs of the formulas for arithmetic progressions
    - Problems on arithmetic progressions
    - Word problems on arithmetic progressions


Also,  you have this free of charge online textbook in ALGEBRA-II in this site
    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Arithmetic progressions".


Save the link to this textbook together with its description

Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson

into your archive and use when it is needed.