(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Prove that the set O = {(y1, y2) : y1 - y2 > 0} is an open subset of R2 in the Euclidean metric.

2. Relevant equations

3. The attempt at a solution

Try as I might I cannot figure out what to take for my r. Any suggestions?

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# Homework Help: Prove set is open using open ball

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