Mathematics

Mathematics

Problem

Which of the following is a necessary condition for the infinite series ∑n=1∞an\displaystyle\sum_{n=1}^{\infty} a_n to converge? a) ∣an∣<1 for every n|a_n|<1\text{ for every }n b) lim⁡n→∞an=0\displaystyle \lim_{n\to\infty} a_n = 0 c) The sequence of partial sums {Sn}\{S_n\} is bounded below. d) The sequence {an}\{a_n\} is strictly decreasing.

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