2.10.94 Number Series

Condition: to explore the sequence for limitations from above, from below, in general (indicate the number in case the sequence is limited) and monotony (increasing, decreasing, non -growing, non -reinforcement), the answer to justify. a) \( a_{n}=\frac{2}{\log _{2}(2 n+1)} \) b) \( a_{n}=\sqrt{n-1} \) c) \( a_{n}=\frac{3}{2+n^{2}} \) d) \ (a_ {n} = \ frac {(-1)^{n+1}} {3} \)