TIFR 2013 Problem 32 Solution is a part of TIFR entrance preparation series. The Tata Institute of Fundamental Research is India’s premier institution for advanced research in Mathematics. The Institute runs a graduate programme leading to the award of Ph.D., Integrated M.Sc.-Ph.D. as well as M.Sc. degree in certain subjects.

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## Problem:True/False

( \lim_{n\to \infty } (n+1)^{1/3} -n^{1/3} = \infty )

## Hint:

Simplify the given expression.

## Discussion:

We feel that ( (n+1)^{1/3} ) goes to infinity at the same speed as ( n^{1/3} ). So in fact, the above limit should be zero.

We make this little bit more rigorous.

( (n+1)^{1/3} -n^{1/3} = \frac{n+1-n}{(n+1)^{2/3}+(n+1)^{1/3}n^{1/3}+n^{2/3} } )

( =\frac{1}{(n+1)^{2/3}+(n+1)^{1/3}n^{1/3}+n^{2/3} } \to 0) as (n\to \infty ).

## Helpdesk

**What is this topic:**Real Analysis**What are some of the associated concept:**Limit of a Sequence**Book Suggestions:**Introduction to Real Analysis by R.G. Bartle, D.R. Sherbert