How do I find the sum of an arithmetic sequence on a calculator?
You can use the following general formula:
where the series has
(Ask a general question, get a general answer.)
Seems that it would be handy to have a closed form expression for the following:
where a and b are constants.
The commutative property of addition says
We can factor the
But we know closed form representations for both of these sums.
Suppose we wanted the following sum:
There are 9 terms in this series so
We want to find
which is, in fact, the sum of the numbers given.