Analysis Problem, limits & supremum, infimum and sequences

  • Thread starter retspool
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  • #1
retspool
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I have analysis quiz tomorrow and i am really poor at sequences.

I dont know where to begin

Let (sn) and (tn) be sequences in R. Assume that (sn) is bounded.

Prove that liminf(sn +tn)≥liminfsn +liminftn,

where we define −∞ + s = −∞ and +∞ + s = +∞ for any s ∈ R.

-thanks
 

Answers and Replies

  • #2
micromass
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Ok, what did you try already?
 
  • #3
retspool
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I got it,

I had to solve a problem before this one which gave me the result
lim infSn = -lim sup(-Sn)

And from a solved example i got

lim Sup(sn + tn) < lim supSn + lim SupTn

so multiplying b.s by (-1) and using -Sn instead for
we get

-lim Sup(-Sn - T) > lim Sup(-Sn) + lim Sup(-Tn)

There fore

lim Inf(Sn + Tn) > lim InfSn + lim InfTn

I had overlooked the solved example.
 

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