Which collections are topologies?

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SUMMARY

The collection {R, empty set, (1,3), (2,4)} is not a topology for the real numbers due to the failure to satisfy the union property; specifically, the union of (1,3) and (2,4) results in (1,4), which is not included in the collection. Additionally, the discussion emphasizes the importance of examining intersections, which was initially overlooked by the participant. A topology must include the union and intersection of its sets, and this collection fails to meet those criteria.

PREREQUISITES
  • Understanding of topology concepts, specifically the definition of a topology.
  • Familiarity with set operations, including union and intersection.
  • Knowledge of real number properties and intervals.
  • Basic mathematical reasoning skills to analyze set collections.
NEXT STEPS
  • Study the formal definition of a topology in mathematical terms.
  • Learn about the properties of unions and intersections in set theory.
  • Examine examples of valid topologies for the real numbers.
  • Explore counterexamples to better understand why certain collections do not form topologies.
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Mathematics students, particularly those studying topology or set theory, as well as educators looking for examples of topology concepts in real analysis.

uncledub
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Homework Statement


Which of the following collections are topologies for the real numbers? If a collection is not a topology for the real numbers, explain why not.


Homework Equations


{R,empty set, (1,3), (2,4)}


The Attempt at a Solution


Not a topology because (1,3) U (2,4) = (1,4)
(1,4) is not in the collection

My hang up on this problem lies in the fact that (1,4) is in the real numbers. But I think all of my answers have to be a member of my original collection.
 
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uncledub said:
But I think all of my answers have to be a member of my original collection.

This is true. Have you examined the intersection of the sets as well?
 
I stopped there because I assumed I could stop after I found it was not true. On my other problems I did examine the intersections as well.

Thank you.
 

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