Q: Compute, without proofs, the suprema and infima of the following sets:
(a) . So, the Sup(A)=3 and Inf(A)=0
(b) I think the interval is , but I am not sure.
(c) . So, Sup(A)=1/2 and Inf(A)=1/3
(d) with . So, Sup(A)=9 and Inf(A)=1/9
I am confused by (b) mostly, but I am not sure about the rest of them either. Do the sup and inf have to be natrual numbers?