Here's the problem:
So I use ratio test (obviously):
. We are taking absolute values; drop the (-1)^n.
After some cancellations I have:
It seems that I could say that cancels,
but then again, n + 1 will increase faster than n. . This is not true.
I can't figure out where to go from here though. .Thanks!
We have: .
Divide numerator and denominator by