(sum \frac{k(-1)^k}{2^k}, k=2 to 5) = (sum \frac{(-1)^k}{2^k}, k=2 to 5) * (sum k, k=2 to 5)

Uh oh! Wolfram|Alpha doesn't run without JavaScript.

Please enable JavaScript. If you don't know how, you can find instructionshere.Once you've done that, refresh this page to start using Wolfram|Alpha.