Question

Let S and T be nonempty subsets of R with the following property: s ≤ t...

Let S and T be nonempty subsets of R with the following property: s ≤ t for all s ∈ S and t ∈ T.

  1. (a) Show that S is bounded above and T is bounded below.

  2. (b) Prove supS ≤ inf T .

  3. (c) Given an example of such sets S and T where S ∩ T is nonempty.

  4. (d) Give an example of sets S and T where supS = infT and S ∩T is the empty set. In your explanation, make sure you justify why sup S = inf T .

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