The second term of a convergent geometric series is 20 and the Fourth term is 5 determine the possible values of the common ratio of the series About the author Skylar

ar = 1/2

a/(1-r) = 4

a = 2-√2

r = 1/4 (2+√2)

or

a = 2+√2

r = 14 (2-√2)