What is the sum of 13 terms if the a_1=-5 and a_n=85 answer

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What is the sum of 13 terms if the a_1=-5 and a_n=85 answer ​

jayleenvania · Answer

Answer:520Step-by-step explanation:First Term a1 = -513th Term a13 = 85Sum of the first n terms of an arithmetic sequence:Sn = n/2(a1 + an) S13 = 13/2 (-5 + 85)S13 = 13/2 (80)S13 = 13 x 40S13 = 520

What is the sum of 13 terms if the a_1=-5 and a_n=85 answer ​

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