Relationship between LUB and GLB in Bounded Functions

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In summary, the conversation discusses a function h from the product of two nonempty sets X and Y to the set R. If the range of h is bounded in R, then two new functions f and g are defined, with f mapping elements of X to the supremum of h for each x, and g mapping elements of Y to the infimum of h for each y. It is then to be proven that the supremum of g for all y in Y is less than or equal to the infimum of f for all x in X. The conversation also mentions that the LUB and GLB exist for h(X,Y) and that A is a subset of h(x,y) for each x, making f(x) less than
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Homework Statement


h: X x Y --> R is a function from X x Y to R. X,Y nonempty. If range is bounded in R. then let

f : X --> R st f(x) = sup{h(x,y): y belongs to Y} (call this set A)
g :Y --> R st g(y) = inf{h(x,y) : x belongs to X} (call this set B)

Then prove that

sup{g(y) : y belongs to Y} is less than or equal to inf{f(x) : x belongs to X}

Homework Equations



none.

The Attempt at a Solution



As h(X,Y) is bounded the LUB and GLB exist. Now for each x, A is a subset of h(x,y). thus f(x) is <= LUB.
thus inf f(x) <= LUB.

Similarly I got, sup g(y) >= GLB.

But this leaves me nowhere :(
 
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well I've got it, thanks anyways.
 

What is the LUB axiom and what does it mean?

The LUB (least upper bound) axiom is a mathematical principle that states that if a set of numbers has an upper bound (a number greater than or equal to all the numbers in the set), then there is a least upper bound for that set (a number that is the smallest of all the upper bounds). In simpler terms, it means that for any set of numbers, there is always a smallest number that is greater than or equal to all the numbers in that set.

Why is the LUB axiom important in mathematics?

The LUB axiom is important in mathematics because it allows us to prove the existence of certain numbers and sets that may not be immediately obvious. It also serves as a foundation for other mathematical principles and proofs.

How is the LUB axiom used in real-life applications?

The LUB axiom is used in various real-life applications, such as in economics, where it is used to determine the maximum price that consumers are willing to pay for a product. It is also used in computer science, particularly in the development of algorithms that require finding the maximum or minimum value in a set of data.

Can the LUB axiom be proven?

No, the LUB axiom cannot be proven. It is considered to be an axiom, which means it is a fundamental truth that is accepted without proof. It is a necessary assumption that allows us to make logical deductions and proofs in mathematics.

What are some other axioms related to the LUB axiom?

Some other axioms related to the LUB axiom include the GLB (greatest lower bound) axiom, which is the dual of the LUB axiom and states that for any set of numbers, there is a greatest lower bound; and the completeness axiom, which is a more general version of the LUB axiom and states that any non-empty set of real numbers that is bounded above has a least upper bound.

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