P V = ∑ k = 1 n C ( 1 + i ) k = C [ 1 − ( 1 + i ) − n i ] {\displaystyle PV=\sum _{k=1}^{n}{\frac {C}{(1+i)^{k}}}=C\left[{\frac {1-(1+i)^{-n}}{i}}\right]}