I have no idea where to start with this one. I tried finding the limits of each, finding the partial sums, I just don't really know how to prove it
Show that
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any help would be appreciated
Did I guess right in correcting your (messy) formula? (you can click on it to see what I wrote)
If so, you should cut the left-hand side sum into two parts: the even (the numerator is -1) and the odd terms (it is +1), and then put both sums together.
Another way (this is the same in fact) is summing the terms two by two: write for the left-hand side.