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  1. If $\displaystyle \left|\sum_{k=0}^\infty a_k\right|\leq M$ Where $M$ is a number, how can you argue that the series is convergent?
  2. If $\displaystyle \sum_{k=0}^\infty a_k=M$ (so your series is convergent), Can you say that $\displaystyle \sum_{k=n+1}^\infty a_k$ also converges?

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