How would I use the definitons to do one of the examples at the bottom?

Big-: Formal Definition Big-e (big theta) For any two functions f.Z R f(n)-6(g(n)) iff [f(n)-O(g(n))JA [f(n)-(g(n))]. (g(n)): the set of all functions satisfying the condition above. o f(n)-(g(n)) meaning: f(n) is bounded above and below by constant scalings of g(n) for large n. Asymptotically speaking, f(n) runs the same as g(n). o Examples: nlog(n) +5n (n log(n))