How do you find the sum of the arithmetic sequence given a1 = 81, an = - 13, n = 20?

batystowy2b 2022-09-12 Answered
How do you find the sum of the arithmetic sequence given a1 = 81, an = - 13, n = 20?
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Answers (1)

Ashlee Ramos
Answered 2022-09-13 Author has 20 answers
The formula for sum of an Arithmetic Sequence when the first term a 1 , number of terms n and last term a n are given is:
S u m = ( n 2 ) ( a 1 + a n )
= 20 2 ( 81 - 13 )
= 10 × 68
= 680

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