Posted by Anonymous on .
find sum of the first 10terms of geometric series with a2=1/2 and r=2

math problem please help 
Reiny,
If a(2) = 1/2 , with r = 1/2
then a(1/2)r = 1/2
and a = 1
now just use the formula
sum(10) = 1( 1  (1/2)^10)/(11/2)
= (1  1/1024)/(1/2)
= 2(1023/1024)
= 1023/512