A Alan S New member May 9, 2010 #1 -101-91-81-71-61......-11-1 Find the sum of the series. I kow the answer is -561 but i want the formula to do so.
-101-91-81-71-61......-11-1 Find the sum of the series. I kow the answer is -561 but i want the formula to do so.
