Data Structures, Algorithms, & Applications in C++
Chapter 3, Exercise 13

If f(n) = Omega(g(n)), then there exist a positive c and an n0 such that g(n)/f(n) <= c for all n >= n0. Hence, the limit of g(n)/f(n) as n goes to infinity is <= c. Next, suppose that the limit of g(n)/f(n) as n goes to infinity is <= c. From this it follows that there is an n0 such that g(n) <= max{1, c} * f(n) for all n >= n0. This proves Theorem 3.4. Theorems 3.2 and 3.4 together imply Theorem 3.6.