Proving Unboundedness of B if A is Unbounded

  • Thread starter Seacow1988
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In summary, to prove unboundedness of B if A is unbounded, you need to show that for any positive number M, there exists a number x in B such that x is greater than M. The relationship between A and B in proving unboundedness is that A must be unbounded in order for B to be unbounded. For example, if A is the set of all positive integers and B is the set of all even integers, since A is unbounded, B is also unbounded. It is not possible for B to be unbounded if A is bounded, as B is a subset of A. Proving unboundedness of B if A is unbounded can have implications in mathematical proofs and real-world applications in
  • #1
Seacow1988
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If A, B are nonempty subsets of R and A is a subset of B, how can you prove that: if A is unbounded, B is unbounded?
 
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  • #2
Suppose to the contrary that B is bounded. So there exists a real number M such that |b| < M for all b in B. Do you see where the problem lies?
 
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  • #3
If you understand the definition of 'boundedness' and 'subset' then this is trivial.
 

FAQ: Proving Unboundedness of B if A is Unbounded

How do you prove unboundedness of B if A is unbounded?

To prove unboundedness of B if A is unbounded, you need to show that for any positive number M, there exists a number x in B such that x is greater than M. This means that B has no upper bound and is therefore unbounded.

What is the relationship between A and B in proving unboundedness?

In order to prove unboundedness of B, you must first know that A is unbounded. This is because if A is bounded, then B cannot be unbounded.

Can you provide an example to illustrate this concept?

Sure, let's say that A is the set of all positive integers and B is the set of all even integers. Since A is unbounded, there is no limit to how large the positive integers can be. This means that B, which is a subset of A, is also unbounded.

Is it possible for B to be unbounded if A is bounded?

No, it is not possible for B to be unbounded if A is bounded. This is because B is a subset of A, so it cannot have a larger limit than A. If A is bounded, then B must also be bounded.

What implications does proving unboundedness of B if A is unbounded have?

If you are able to prove unboundedness of B if A is unbounded, then it means that B has no upper bound and can potentially grow infinitely. This can be useful in mathematical proofs and can have real-world applications in fields such as economics and physics.

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