SOLUTION: Find sum of first 100 terms of an arithemetic sequence with 15th term of 86 and first term of 2

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Question 1017338: Find sum of first 100 terms of an arithemetic
sequence with 15th term of 86 and first term of 2

Answer by Edwin McCravy(20056) About Me  (Show Source):
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Find sum of first 100 terms of an arithmetic
sequence with 15th term of 86 and first term of 2. 

an = a1 + (n-1)d

86 = 2 + (15-1)d

84 = 14d

84%2F14 = d 

6 = d

Sn = n%2F2[2a1 + (n-1)d] 


S100 = 100%2F2[2(2) + (100-1)6]

S100 = 50[4 + (99)6]

S100 = 50[4 + 594]

S100 = 50[598]

S100 = 29900

Edwin