Strategy for Testing Series

  1. Image Upload 1
    • p-series
    • convergent if p>1
    • divergent if p≤1
  2. Image Upload 2 or Image Upload 3
    • geometric series
    • converges if |r|<1
    • diverges if |r|≥1
  3. An is a rational function or algebraic function of n (involving roots of polynomials)
    • comparison test with p-series
    • the value of p should be chosen by keeping only the highest powers of n in the numerator and denomiator
    • (i) Convergence: If Σbn is convergent, and an ≤ bn for all n, then Σan is convergent;
    • (ii) Divergence: If Σbn is divergent, and an ≥ bn for all n, then Σan is divergent.
    • NOTE: Comparison test only applies to series with positive terms. If it has negative terms, test for absol convergence.
  4. If series is similar to geo series
    • comparison test with geo series
    • NOTE: Comparison test only applies to series with positive terms. If it has negative terms, test for absol convergence.
  5. Image Upload 4
    Test for Divergence
  6. Image Upload 5 orImage Upload 6
    • Alternating Series Test
    • (i) bn+1 ≤  bn for all n, and
    • (ii) Image Upload 7,then the series is convergent.
  7. series with factorials, products (a constant raised to the nth power
    • Ratio test
    • (i) If Image Upload 8 < 1, then the series Σan is absolutely convergent(and therefore convergent)
    • (ii) If Image Upload 9 >1or Image Upload 10, then Σan is divergent
    • (iii) If Image Upload 11=1, the Ratio Test is inconclusive.

    NOTE: Image Upload 12 as n→ ∞ for all p-series.
  8. Image Upload 13
    Harmonic series. Diverges
  9. an is of the form (bn)n
    • Root Test
    • (i) If Image Upload 14< 1, then Σan is absolutely convergent (and therefore convergent)
    • (ii) If Image Upload 15> 1, or Image Upload 16, then Σan is divergent
    • (iii) If Image Upload 17, the Root Test is inconclusive.
  10. If Image Upload 18, where Image Upload 19 is easily evalutated
    • Integral Test
    • If if f is cts, positive and decreasing fcn on [1,∞), and an=f(n), then the series is convergent IFF Image Upload 20 is convergent
  11. If series is similar to p-series or geometric series
    • Limit Comparison Test
    • Given the series Σan, Σbn with positive terms,if Image Upload 21, where c > 0 and finite, then the two series either both converge or both diverge.
Author
Jamie_Bee
ID
291067
Card Set
Strategy for Testing Series
Description
Strategy for Testing Series
Updated