Show that ∞∑n=1n−√nn2+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 n−√nn2+5n∼1n Conclude using limit comparison test.
EDIT Updated on the request of OP
n−√nn2+5n=1−1/√nn+5=1n(1−1/√n1+5/n)⏟→1 as n→∞
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