i added the question in the link:

http://img388.imageshack.us/img388/2220/57946210jf5.gif

this is a total abstract thing

i dont know how to prove SUP whithout a formula to the series

i need to prove that S is the least upper bound

i dont know how to do that. i can say that

there is a cetain "e"

that if we subtract it from S we will get a member from A which is larger then S.

but is it a proof??

and what the -> thing means in the end ??