Let A be a nonempty set of real numbers which

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SUMMARY

The discussion centers on proving that for a nonempty set of real numbers A, which is bounded below, the infimum of A is equal to the negative of the supremum of the set -A, defined as all real numbers -x where x is in A. The key concepts involved include the definitions of upper bounds, lower bounds, least upper bounds, and least lower bounds. The proof requires deriving a contradiction based on the assumption that a certain value, gamma, is an upper bound for -A.

PREREQUISITES
  • Understanding of real number sets and their properties
  • Familiarity with the concepts of infimum and supremum
  • Knowledge of upper and lower bounds in mathematical analysis
  • Experience with proof techniques, particularly contradiction
NEXT STEPS
  • Study the definitions and properties of infimum and supremum in real analysis
  • Learn about the completeness property of real numbers
  • Explore proof techniques involving contradiction in mathematical proofs
  • Investigate examples of bounded sets and their infimum and supremum
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Mathematics students, particularly those studying real analysis, and educators looking for examples of proofs involving bounds and infimum/supremum concepts.

Jamin2112
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Homework Statement



Let A be a nonempty set of real numbers which is bounded below. Let -A be the set of all real numbers -x, where x is in A. Prove that inf A = -sup(-A).

Homework Equations



Definitions of upper bound, lower bound, least upper bound, and least lower bound.

The Attempt at a Solution



Here's what I have so far:


Ex5.png



Almost there! I just need to derive a contradiction on my assumption that gamma is an upper bound for -A.
 
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[URL]http://www.threadbombing.com/data/media/8/bummmp.gif[/URL]
By the way, if you help me with this problem I'll give you another one.
 
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