# Math Help - Bases for topologies

1. ## Bases for topologies

Hello i need yours help!!

Show that the class of closed intervals [a,b], where a and b are rational and a<b, is not a base for a topology on the real line R

2. Originally Posted by Debor
Hello i need yours help!!

Show that the class of closed intervals [a,b], where a and b are rational and a<b, is not a base for a topology on the real line R
Suppose that a<b<c, and consider the intersection $[a,b]\cap[b,c]$.

3. Originally Posted by Debor
Hello i need yours help!!

Show that the class of closed intervals [a,b], where a and b are rational and a<b, is not a base for a topology on the real line R
How do you define base? What topology?