Sum of the following segma notation- The upper limit is ∞ the lower limit index is n=1 and the general term is 5(0.2)^2 The fiirst 3 terms I figure to be 1,.2,.04,.008 How to find sum when its ∞?  

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The formula for an infinite geometric series is a÷(1-r) where a is the first term and r is the number being raised to a power. In your problem a = 1 and r = .2 so S = 1÷(1-.2) = 1.25