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Mathematics 21 Online
OpenStudy (anonymous):

series questions

OpenStudy (anonymous):

OpenStudy (anonymous):

@amistre64

OpenStudy (amistre64):

the integral test is pretty much change n to x and integrate

OpenStudy (amistre64):

n^4/n^6, since the bottom is bigger degree than top, the sequence an goes to zero

OpenStudy (amistre64):

cant say i know what tests to choose tho :/

OpenStudy (anonymous):

so 5 converges right and what is the test you used?

OpenStudy (amistre64):

5 converges and the limit of an IS 0, but yeah, i got no solid on the tests used.

OpenStudy (anonymous):

do you know anyone who can help me with this? I really dont know how to do this.

OpenStudy (amistre64):

the next one, a test cant converge and diverge at the same time; and a test will either be converge, diverge, or inconclusive

OpenStudy (anonymous):

I just tried that and its wrong.

OpenStudy (amistre64):

which one you try?

OpenStudy (anonymous):

number 6

OpenStudy (amistre64):

yeah, which option?

OpenStudy (anonymous):

2nd option

OpenStudy (amistre64):

why?

OpenStudy (amistre64):

i said: a test cant converge and diverge at the same time; and a test will either be converge, diverge, or inconclusive

OpenStudy (anonymous):

you said the series converges and diverges at the saem time right

OpenStudy (anonymous):

oh sorry I read that wrong

OpenStudy (anonymous):

so which option is it?

OpenStudy (anonymous):

it can be more than one

OpenStudy (amistre64):

a little self reflection here. ive given ample hints for it :)

OpenStudy (anonymous):

you said it can either converge diverge or be inconclusive. However I dont think the first option is right since comparision test doesnt take precedence so is it option 4

OpenStudy (amistre64):

option 4 is what im thinking, the analysis is in errorsince one test says converge, the other says diverge

OpenStudy (amistre64):

3 may be plausible, but i dont think its the most accurate

OpenStudy (amistre64):

it may be possible to determine if the analysis is done correctly

OpenStudy (anonymous):

4 is correct.

OpenStudy (amistre64):

yay!! :)

OpenStudy (anonymous):

do you know how to get the associated function for 3?

OpenStudy (amistre64):

i believe, like i posted, change n to x

OpenStudy (anonymous):

do I need to add +C to the answer?

OpenStudy (amistre64):

no, its asking for the function that gets integrated, not for the integration itself

OpenStudy (amistre64):

\[\sum f(n)\to\int f(x)\]

OpenStudy (anonymous):

I did that and I got it wrong I got 1/2tan^-1(x)^2

OpenStudy (amistre64):

f(x) is more compact; if it converges then the f(n) would have to converge as well

OpenStudy (amistre64):

\[\frac{tan^{-1}(x)}{x^2+1}\]

OpenStudy (anonymous):

yeah I took the indefinite integral of that

OpenStudy (amistre64):

it doesnt ask you to do that

OpenStudy (anonymous):

what does it ask then?

OpenStudy (amistre64):

it asks what function of x you would use to integrate ....

OpenStudy (anonymous):

Ok I understand now.

OpenStudy (amistre64):

for example:\[\sum n^2\to\int x^2~dx\] f(n) = n^2; f(x) = x^2

OpenStudy (anonymous):

ok here is another problem I dont get

OpenStudy (amistre64):

id suggest doing a root test on it

OpenStudy (anonymous):

it converges

OpenStudy (amistre64):

lim |n^(2/n) pi/4 |

OpenStudy (amistre64):

the limit is about 3/4 right?

OpenStudy (anonymous):

no its 0

OpenStudy (amistre64):

it helps to actually take the root test

OpenStudy (amistre64):

and the next one, i dont htink factorials are well suited to root tests

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