送交者: lakeblue 于 December 18, 2009 22:40:08:
回答: 10^2+10^4+....+10^(2N) = (100/99)10^(2N) - (199/99). 由 lala 于 December 18, 2009 13:24:26:
The sum of the first N-1 terms only contributes a very small correction to the answer when N ~ 270, as can be seen from the above expressions you gave.