- #1
AdrianZ
- 319
- 0
Homework Statement
consider the set A={1/n+1/m: n,m are natural numbers}. find A'
The Attempt at a Solution
I don't know what the problem is asking me. I don't know what A' represents here. I assume that A' stands for the set of the limit points of A because this is an Analysis problem and Rudin's Analysis use that notation for the set of all limit points. but I'm not 100% sure. Does anyone know what A' represents here?
If A' stands for the set of all limit points, then what should I do to find all the limit points of A? I know that 0 is a limit point of the set, because any open ball (with arbitrary radius) centered at 0 contains an infinite number of points in the neighborhood and I can show that in a fairly easy way. but I don't know whether there are other limit points or not. I guess 0 is the only limit point of the set if the metric space that we're working with is Real numbers. but how can I prove that? I guess I need to show that for any other real number, I can find delta such that the neighborhood of that number within the radius delta contains only a finite number of points in A and therefore that real number can not be a limit point of A. am I right?