SOLUTION: I need help finding the sum of this arithmetic series. Image of arithmetic series: https://i.imgsafe.org/6dd8440ee3.png A.) 25 B.) 126 C.) 133 D.) 119

Algebra ->  Finance -> SOLUTION: I need help finding the sum of this arithmetic series. Image of arithmetic series: https://i.imgsafe.org/6dd8440ee3.png A.) 25 B.) 126 C.) 133 D.) 119       Log On


   

Question 1040931: I need help finding the sum of this arithmetic series.
Image of arithmetic series: https://i.imgsafe.org/6dd8440ee3.png
A.) 25
B.) 126
C.) 133
D.) 119

Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
S%5BN%5D=%28N%2F2%29%28a%5B1%5D%2Ba%5Bn%5D%29
or in this case,
S%5B7%5D=%287%2F2%29%28a%5B1%5D%2Ba%5B7%5D%29
,
,
a%5B1%5D=2%281%29%2B11=2%2B11=13
a%5B7%5D=2%287%29%2B11=14%2B11=25
So then,
S%5B7%5D=%287%2F2%29%2813%2B25%29
S%5B7%5D=%287%2F2%29%2838%29
S%5B7%5D=133