define

  • define
  • And the item before NNN
  • Determine convergence
  • Sum: sum of the first n terms as n→∞n\to \inftyn→∞
  • diverse series has no sum

Classic series

  • Geometric series geometric
  • Harmonic series harmonic
  • collapsing series

The nature of the

  • ∑ n = 1 up \ sum ^ \ infty_ {n = 1} ∑, n = 1 up convergence is lim ⁡ n – > + up an = 0 \ lim_ {n \ \ infty} to + a_n = 0 limn – + up an = 0

  • Lim ⁡ n – > + up an = 0 \ lim_ {n \ \ infty} to + a_n = 0 limn – + up an = can’t launch ∑ 0 n = 1 up \ sum ^ \ infty_ {n = 1} ∑ n = 1 up convergence

  • Series are linear (additivity and multiplicability)

  • The sum of convergent series converges, but the sum of divergent series does not necessarily diverge