Let S be an ordered set and A is a nonempty subset such that sup A exists. Suppose there is a B⊂A such that whenever x∈A there is a y∈B such that x≤y. Show that supB exists and supB=supA.

Lipossig

Lipossig

Answered question

2020-11-30

Let S be an ordered set and A is a nonempty subset such that sup A exists. Suppose there is a BA such that whenever xA there is a yB such that xy. Show that B exists and B=⊃A.

Answer & Explanation

timbalemX

timbalemX

Skilled2020-12-01Added 108 answers

Given that BA. Since (A) exist therefore A has an upper bound sya a then a is also an upper bound of B. Therefore (B) exist and On the order hand for every xA there exist yB such that xy. Therefore xy≤⊃(B). Hence (A)≤⊃(B) Therefore from (1) and (2) (A)=⊃(B).

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