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 P: 159 1. The problem statement, all variables and given/known data Suppose that $$\sum$$anxn has finite radius of convergence R and that an >= 0 for all n. Show that if the series converges at R, then it also converges at -R. 2. Relevant equations 3. The attempt at a solution Since the series converges at R, then I know that $$\sum$$anRn = M. At -R, the series is the following: $$\sum$$an(-R)n = $$\sum$$(-1)nanRn. I'm not sure where to go from here. I thought I needed to use the alternating series test, but how can I know that a1 >= a2 >= ... >= an for all n? Do I know this because the series converges? Thanks for your help.