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Math and science::Analysis::Tao::07. Series

The Root Test

Let \( \sum_{n=m}^{\infty}a_n \) be a series of real numbers and let [ \( \alpha = ? \) ].

  1. If \( \alpha < 1 \), then the series \( \sum_{n=m}^{\infty}a_n \) is absolutely convergent (and hence conditionally convergent).
  2. If \( \alpha > 1 \), then the series \( \sum_{n=m}^{\infty}a_n \) is not conditionally convergent (and hence is not absolutely convergent either).
  3. If \( \alpha = 1 \), this test does not assert any conclusion.

The famous Root Test.