Problem 137 (difficulty: 2/10)

Are the following sets bounded from above or from below? What is the maximum, minmimum, supremum and infimum? Which set is convex?

\(\displaystyle \emptyset \qquad \{1,2,3,\dots\} \qquad \{1,-1/2,1/3,-1/4,1/5,\dots\} \qquad \Q \qquad \R \qquad [1,2) \qquad (2,3] \qquad [1,2)\cup(2,3] \)

Give me another random problem!