https://adamaths.com/forum/
10050020040
https://adamaths.com/forum/viewtopic.php?f=77&t=2667
Page
1
of
1
10050020040
Posted:
Mon Oct 16, 2017 7:17 pm
by
ada
$\sum_{x=0}^n r^x = \frac{1-r^{n+1}}{1-r}$, $r\neq1$