
Jacob D. answered 06/07/20
Master's in mathematics with calculus teaching experience
Looks like your posting a lot of questions at once, so I'll give you a hint. First, what is the nth root of (-3/ arctan(n))^n? Once you find that, it may be helpful to know lim n →∞ arctan(n), think about the graph of arctan(x). Now use the root test and see what you get!