Posted by kaela on Friday, January 4, 2013 at 2:35pm.
Sn = a(1-r^n)/(1-r), so
(1-r^4)/(1-r^8) = 1/17
r^4 = 1 or 16
1 is no good, so r=2
this will hold, regardless of the first term, T1. Letting T1=1, we have
1,2,4,8,16,32,64,128...
S4 = 15
S8 = 255
S4/S8 = 1/17
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