How do you find the sum of the arithmetic sequence given a1=58, an=-7, n=26? Precalculus Series Sums of Arithmetic Sequences 1 Answer seph Dec 30, 2016 #S_26 = 663# Explanation: #S_n = (A_1 + A_n)n/2# #=> S_26 = (58 + -7)26/2# #=> S_26 = 51*13# #=> S_26 = 663# Answer link Related questions How do I find the sum of an arithmetic sequence? What is the formula for the sum of an arithmetic sequence? What are common mistakes students make when finding the sum of an arithmetic sequence? How do I find the sum of an arithmetic sequence on a calculator? How do I find the partial sum of an arithmetic sequence? How do I find the partial sum of an arithmetic sequence on a TI-84? What is meant by the sum of an arithmetic sequence? How do I find the sum of the arithmetic sequence 3, 5, 7, 9, ..., 21? What is the sum of the arithmetic sequence 22, 13, 4? How do you find the sum of the first 25 terms of the sequence: 7,19,31,43...? See all questions in Sums of Arithmetic Sequences Impact of this question 3217 views around the world You can reuse this answer Creative Commons License