General topology: Prove a Set is Open

[PeroK]

What's wrong?

Come on! If you take a positive number away what you have gets smaller.

 

[lep11]

Come on! If you take a positive number away what you have gets smaller.

Okay, true.

I might just give up. I am not smart enough to study crap like this.

 

[lep11]

Okay, true.

I might just give up. I am not smart enough to study crap like this.

I took a break and tried again.

$d(0,z)≥d(0,x)-d(x,z)≥r+1-d(x,z)>r+1-r=1$

 

[lep11]

Thank You PeroK!