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Mathematics 18 Online
OpenStudy (anonymous):

at http://tutorial.math.lamar.edu/Classes/CalcII/ImproperIntegralsCompTest.aspx in the second example it says that int (upper limit inf & lower limit 3) 1/x dx diverges by the fact that the power of the denominator is > 1 but then immediately after this statement in this example it says "We’ve got a larger function that is divergent" which contradicts that it diverges, so is it like a printing mistake (typo) or am I wrong to understand it?

OpenStudy (anonymous):

anyone please help me :(

OpenStudy (phi):

The statement says *probably* will converge. 1/x does not converge (but it's close)

OpenStudy (anonymous):

in the scond example?

OpenStudy (phi):

so he's looking for a function that is larger than 1/x^p that does converge.

OpenStudy (anonymous):

diverges by the fact that \[p\leq 1\]

OpenStudy (phi):

Yes if the integrand goes to zero faster than 1/x then the integral will probably converge

OpenStudy (phi):

1/x is the harmonic series, and it diverges very very slowly

OpenStudy (anonymous):

so 1/x+e^x<1/x<1/e^x

OpenStudy (anonymous):

so according to this 1/e^x is a greater function that others

OpenStudy (anonymous):

sorry i am lost

OpenStudy (phi):

1/e^x converges so it is < 1/x

OpenStudy (anonymous):

okkkkkkk

OpenStudy (phi):

and 1/(x+e^x) < 1/e^x so it also converges.

OpenStudy (anonymous):

but then 1/x also converges so by the comparison test it is fine then it says in the example that "We’ve got a larger function that is divergent" (just copy and find ctrl+f on that website

OpenStudy (phi):

no, 1/x diverges

OpenStudy (anonymous):

how?

OpenStudy (anonymous):

okkkkkkkkkkkkkk got it if p<= 1 then diverges

OpenStudy (anonymous):

got it

OpenStudy (anonymous):

thanks a tonne bro

OpenStudy (phi):

It's not really too complicated.

OpenStudy (phi):

just confusing.

OpenStudy (anonymous):

i was not reading it properly i was reading it as converging :}

OpenStudy (phi):

1/x was famous back in the day. All kinds of arguments about if it converged or not.

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