We have a, b ∈ R \ Q, a < b.
A = {x ∈ Q: a < x < b}
Show that A is clopen(open and close) in Q
i have being trying to solve this problem in the last 2hours
i need some hints or examples
thank you in advance
Assuming you give the topology inherited from then open sets in are those of the form where is open in . Is open? fails to be closed in because it lacks and , but is that a problem in ?
Assuming you give the topology inherited from then open sets in are those of the form where is open in . Is open? fails to be closed in because it lacks and , but is that a problem in ?