SOLUTION: Write the following series in sigma notation 12+7+2+.........up to 7 terms

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Question 626886: Write the following series in sigma notation
12+7+2+.........up to 7 terms
Found 2 solutions by richard1234, jim_thompson5910:
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
Arithmetic sequence, common difference -5.




Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
You're subtracting 5 each time. The first 7 terms are

12+7+2+(-3)+(-8)+(-13)+(-18)

The nth term is 12+(n-1)*(-5) which becomes -5n+17

So the sum of the first 7 terms using sigma notation is


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