SOLUTION: If an = 3n + 4, find the sum of the first 20 terms in the sequence.

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Question 1141644: If an = 3n + 4, find the sum of the first 20 terms in the sequence.
Answer by ikleyn(52788)   (Show Source): You can put this solution on YOUR website!
.
It is arithmetic progression with the first term  = 7, the common difference d = 3 and the number of terms n = 20.


Use the formula for the sum of the first "n" terms of an AP


     = .


Substitute the given values into the formula


     = .


Now use your calculator (or computer) to get the numerical value.



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    - Arithmetic progressions
    - The proofs of the formulas for arithmetic progressions
    - Problems on arithmetic progressions
    - Word problems on arithmetic progressions
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The referred lessons are the part of this online textbook under the topic "Arithmetic progressions".


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Free of charge online textbook in ALGEBRA-II
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