SOLUTION: Give the arithmetic series (1,2,3,...,38,39,40)

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Question 1088375: Give the arithmetic series
(1,2,3,...,38,39,40)
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
(1,2,3,...,38,39,40)
first term a%5B1%5D=1
second term a%5B2%5D=3
difference d=2-1=1
second term a%5B2%5D=3
third term a%5B3%5D=3
difference d=3-2=1

so, the terms have a common difference d=1, and this is indeed an arithmetic sequence.
The last term in the partial sum will be:
a%5Bn%5D=a%5B1%5D%2B%28n-1%29d...since d=1
a%5Bn%5D=a%5B1%5D%2B%28n-1%29