I am having trouble with a simple question : Consider $\bar{R}$ the extended real line and $ 0 < q < \infty$.

Let $x_n $a sequence in $\bar{R}$ with $x_n \geq 0, \forall \ n $. Suppose that $x_n \rightarrow a$ where $a = + \infty$

What I can say about the limit below?

$lim_{n \rightarrow + \infty} (x_n)^{\frac{-1}{q}}$


HINT: Let $p=\dfrac1q$; clearly $0<p<\infty$. For sufficiently large $n$, $x_n\ne 0$, and $x_n^{-p}=\dfrac1{x_n^p}$ actually makes sense. Now what is $\lim\limits_{n\to\infty}x_n^p$?

  • $\begingroup$ your suggestion solves the problem ^^ .thank you! $\endgroup$ – math student May 9 '13 at 2:56
  • $\begingroup$ @Leandro: You’re welcome. $\endgroup$ – Brian M. Scott May 9 '13 at 2:57

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