Wednesday, August 24, 2016

sequences and series - Show that sumlimitsinftyn=1fracnsqrtnn2+5n diverges


Show that n=1nnn2+5n  diverges.


I have tried Root test, Ratio Test, Cauchy condensation Test but all have failed. I think this has to be done by Comparison Test or Limit Comparison Test. But what is the suitable form it has to be reduced to?


Answer




Note that nnn2+5n1n Conclude using limit comparison test.



EDIT Updated on the request of OP


nnn2+5n=11/nn+5=1n(11/n1+5/n)1 as n


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