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[phpBB Debug] PHP Warning: in file [ROOT]/phpbb/session.php on line 580: sizeof(): Parameter must be an array or an object that implements Countable
[phpBB Debug] PHP Warning: in file [ROOT]/phpbb/session.php on line 636: sizeof(): Parameter must be an array or an object that implements Countable
•10050020050

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10050020050

Posted: Mon Oct 16, 2017 7:18 pm

by ada

$\sum_{x=0}^n ar^x = \frac{a(1-r^{n+1})}{1-r}$,&emsp;$r\neq1$