3. Suppose the sequence {an} is strictly monotonically decreasing and bounded below by 3. (That is, 3 is a lower bound of the set of values {an n E N}. ) (a) (10 points) Prove that -3 is an upper bound of the set {-an | n E N}. (b) (10 points) Prove that -a1 is the infimum of the set {-an n e N}. (Hint: One could prove this by showing -aj to be the minimum of the set {-an | n e N}) |