Wednesday, June 15, 2016

calculus - How can a sum converge if it has a singularity?



Problem 32 on page 630 in Larson Calculus 9e.




In Exercies 29-36, test for convergence or divergence, using each test at least one. Identify which test was used.

32.n=21n38




when n=2 a2=1238=10 Uh, not possible to divide by zero.



I know it converges for n=31n38=13



But what is *Undefined*+13= ????



From the comments, it is very likely a typo.




Thus, I will present some problems for more clearity.



n=01n38=13 Will not converge because at n=2 there is singularity?



Aka, No series can converge if there exist a singularity?


Answer



In this case, as many pointed out, it seems like a typo.



Regarding:





Thus, I will present some problems for more clearity.



n=01n38=13 Will not converge because at n=2 there is singularity?



Aka, No series can converge if there exist a singularity?




Notice that




n=01n38=13



is just a (no sense) formula, so it cannot converge or diverge.



The question




Does




k=0ak



converge?




It's a shorthand for




Does the sequence




(nk=0ak)nN



converge?




In this case



(nk=01k38)nN



doesn't even makes sense, you have already noted why, so it can't converge nor diverge.



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