I have two similar questions:

1.) Sigma from n=1 to infinity (1 / (sqrt(n) * (ln n)^4))

2.) Sigma from n=1 to infinity ((ln n)^3 / n^2)

I must use the direct comparison/limit comparison tests for these, but I'm not sure how to go about choosing a bn.

My first intuition for #1 was to choose bn to be 1/n, but 1/n is divergent and greater than (1 / (sqrt(n) * (ln n)^4)).

Any help would be appreciated because I'm very lost.