# Unbounded Subset

## Main Question or Discussion Point

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?

## Answers and Replies

gb7nash
Homework Helper
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?

Last edited:
Landau
Science Advisor
If you understand the definition of 'boundedness' and 'subset' then this is trivial.