I am confused on the following series:
∞∑n=11n(n+1)=1
My calculator reveals that the answer found when evaluating this series is 1. However, I am not sure how it arrives at this conclusion. I understand that partial fractions will be used creating the following equation. I just don't understand how to proceed with the problem.
∞∑n=1(1n−1n+1)=1
Answer
Write out a few terms of the series. You should see a pattern! But first consider the finite series:
m∑n=1(1n−1n+1)=1−12+12−13+13−14+⋯+1m−1−1m+1m−1m+1.
This sum is telescoping, since it collapses like a telescope.
Everything is left except for the first and last term. Now what's the limit as m→∞?
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