Series tests

by jvadair

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Geometric series converge when

0<\left|r\right|<1\ \ for\ \sum_{n=0}^{\infty}ar^n

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11 cards

1

Geometric series converge when

0<\left|r\right|<1\ \ for\ \sum_{n=0}^{\infty}ar^n

2

Sum of a geometric series

\frac{a}{1-r}

3

A series diverges by nth term test when

\lim n\rightarrow\infty\left(a_n\ne0\right)\ for\ \sum_{n=1}^{\infty}a_n

4

A series converges by the integral test when

\int_0^{\infty}f\left(x\right)dx\ \ is\ positive\ \&\ finite

5

The integral test only works when

f(x) is positive, continuous, and decreasing

6

A series converges by the p-series test when

p\ >\ 1\ for\ \sum_{n=1}^{\infty}\frac{1}{n^p}

7

Direct comparison test

If a larger function (0 < f1 <= f2) converges/diverges, then the smaller one does too.

8

The direct/limit comparison tests only work if

The series has all positive terms

9

Limit comparison test

If\lim n\rightarrow\infty\left(\frac{a_n}{b_n}\right)>0,\ the\ a_n\ series\ does\ the\ same\ as\ the\ b_n

10

Alternating series test

Converges\ if\ \lim n\rightarrow\infty\left(a_n\right)=0\ \&\ \left|a_{n+1}\right|<\left|a_n\right|

11

Ratio test

Converges\ if\ \lim n\rightarrow\infty\left|\frac{a_{n+1}}{a_n}\right|<1,\ diverges\ if\ it's\ >\ 1