SOLUTION: Will someone please help me. I don't know where to begin on this problem. I have to show all my work. Find Sn for the arithmetic series in which A1=-11, An=13, and n=7. I have

Algebra ->  Sequences-and-series -> SOLUTION: Will someone please help me. I don't know where to begin on this problem. I have to show all my work. Find Sn for the arithmetic series in which A1=-11, An=13, and n=7. I have       Log On


   

Question 171173: Will someone please help me. I don't know where to begin on this problem. I have to show all my work.
Find Sn for the arithmetic series in which A1=-11, An=13, and n=7.
I have a big test later today and really need help.
Thanks
Answer by monika_p(71) About Me  (Show Source):
You can put this solution on YOUR website!
Formula for an arithmetic series is:

Sn=%28A1+%2B+An%29%2An%2F2
You have given A1 = -11
An = 13
n = 7
substitute and simplify :
Sn+=+%28-11+%2B+13%29%2A+7%2F2
Sn+=+2%2A7%2F2
The answer is:
Sn = 7