CHAPTER 9-H STRATEGIES FOR TESTING SERIES
StrategiesClassify the series to determine which test to use.
1. If then the series diverges.
This is the nth Term Test for divergence.
2. Look to see if the series is a p-series . If so it will converge if p > 1 and diverge if p ≤ 1.
3. Look to see if the series is a geometric series.
If so it will converge if r < 1. If r ≥ 1 then it will diverge. ( you may need to manipulate the series algebraically to get it into the proper form)
lim 0nna
pn1
1-nn aror ar
Strategies cont.
4. If your series is similar to a p-series or a geometric series try a comparison test. Applies
only to series with positive terms
5. If the terms of your series alternate between positive and negative
try the alternating series test.
nnn a1-or a1 n
1
Strategies cont.
6. If your series contains factorials or a constant raised to the power n try the ratio test (but don’t bother with the ratio test for a p-series).7. If the series is of the form Ʃ(bn)n try the
root test.
8. If an = f(n) where is easily
evaluated try the integral test.
9. Telescoping series: write out series and cancel terms
1
f x dx
1
12 1
Can best be evaluated by1. direct comparison test
2. limit comparison test
3. test for divergence
4. hoping for a fire drill right now
n
nn
1.
1
1
3
1 8
Can best be evaluated using1. root test
2. ratio test
3. integral test
4. alternating series test
n n
nn
n
n
2.
2 cont. Find the limit
21
125
Can best be evaluated using1. ratio test
2. root test
3. integral test
4. alternating series test
n
n
nn
3.
2
31
11
Can best be evaluated using1. direct comparison test
2. limit comparison test
3. ratio test
4. ask the teacher
n
nn
4.
3
2
Using the limit comparison test we can compare the terms in our series with
11.
12.
13.
14.
n
n
n
n
4. cont.
2
311The lim is1
1. 1
2. 0
3.
4. DNE
n
nn
n
4. cont
1
21
Can best be evaluated by 1. direct comparison test
2. integral test
3. root test
4. test for divergence
n
n
en
5.
1
21
The integral can be evaluated using
1. integration by parts
2. trigonometric substitution
3. partial fraction decomposition
4. substitution
xe dxx
5. cont
The result of the integration is1. 1 converges
2. 1 converges
3. diverges
4. 0 diverges
e
e
5. cont
1
2!
Can best be evaluated using1. ratio test
2. test for divergence
3. limit comparison test
4. direct comparison test
n
n n
6.
1The ratio of is
1. 2
22.
23. 1
14. 2
n
n
aa
k
k
k
k
6. cont
2 1
1
3
Can best be evaluated by 1. test for divergence
2. limit comparison test
3. ratio test
4. root test
n
nn n
7.
8. Determine the convergence or divergence of the series
1 121
n nn
9. Determine the convergence or divergence of the series
123
3
2431
n nnn
10. Determine the convergence or divergence of the series
1
2
n
nne
11. Determine the convergence or divergence of the series
14
3
11
n
n
nn
12. Determine the convergence or divergence of the series
1 321
nn
HOME WORKWorksheet 9-H
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