How can I solve this limit?
thanks you!!!
You can easily look up manual, and employ
Limit[Sum[k*Sqrt[k], {k, 1, n}]/(Sqrt[n]*Sum[2*k - 1, {k, 1, n}]),
n -> Infinity]
(* 2/5 *)
Also track the dependence of the limit on parameter (u) using
ListPlot[Table[{u,
Limit[Sum[k*Sqrt[k], {k, 1, n}]/(Sqrt[n]*Sum[u*k - 1, {k, 1, n}]),
n -> Infinity]}, {u, 1, 4, 0.1}]]
The arrow indicates value corresponding to u=2