1. The problem statement, all variables and given/known data I should know this (it's been a few years) but can't seem to get the answer for: Ʃ (from i = 0 to n) 0.5-i the answer is apparently 2n+1-1 / 2 - 1 how do I go about getting this? 2. Relevant equations I tried Ʃn-1k=0ark = a* 1-rn / 1 - r with no luck 3. The attempt at a solution = a* 1-rn+1 / 1 - r (which is wrong) Thanks very much!