SOLUTION: find the sum of the following arithmetic series and write in summation notation http://prntscr.com/sfire3

Algebra ->  Sequences-and-series -> SOLUTION: find the sum of the following arithmetic series and write in summation notation http://prntscr.com/sfire3      Log On


   

Question 1158911: find the sum of the following arithmetic series and write in summation notation
http://prntscr.com/sfire3
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

a.
4,11,...
since you have arithmetic series, the common difference is+d=7
the sum of first 16 terms formula is
a%5B1%5D=4
d=7
n=16
S%5Bn%5D=%28n%2F2%29%282a%5B1%5D%2Bd%28n-1%29%29.....substitute given values
S%5B16%5D=%2816%2F2%29%282%2A4%2B7%2816-1%29%29
S%5B16%5D=%2816%2F2%29%282%2A4%2B7%2815%29%29
S%5B16%5D=8%28113%29
S%5B16%5D=904



c.
3,8%261%2F2,...
a%5B1%5D=3
d=5.5
n=20
S%5Bn%5D=%28n%2F2%29%282a%5B1%5D%2Bd%28n-1%29%29
S%5B20%5D=%2820%2F2%29%282%283%29%2B5.5%2820-1%29%29
S%5B20%5D=10%286%2B5.5%2A19%29
S%5B20%5D=10%28110.5%29
S%5B20%5D=1105