SOLUTION: Find the sum of the first nine terms of the arithmetic series. 2 - 5 - 12 - 19 - ...

SOLUTION: Find the sum of the first nine terms of the arithmetic series. 2 - 5 - 12 - 19 - ...

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Question 142142: Find the sum of the first nine terms of the arithmetic series.
2 - 5 - 12 - 19 - ...
Answer by nabla(475) (Show Source): You can put this solution on YOUR website!
The sum of the first n terms of an arithmetic progression is .
n=9 <--- # of terms
a=2 <--starting term
r=-7 <--- common difference between terms

s=
=

We can check by iterating every term:
2-5-12-19-26-33-40-47-54=-234
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