Geometric Series

[gaunt pasture]

Should the series include the (-1)ˆk?

[gaunt pasture]

I'm guessing there's a mistake somewhere but I'm not really sure where

[rotund path]

I guess the mistake its in the summation operator

Since You are multiplying 2 infinity series

It does not merge like that since its a double sum

[gaunt pasture]

Thank you, I tried it with some terms and the -1 eventually disappears

.solved