I'm reading around big O to get some concept about performance for data structures. The mathematics book recommended by the open book ~ maths for computer science
In the book (pg 456) part of the pre-requisite knowledge to understand big oh are approximate sums.
I'm struggling to get my head around some of the concepts presented in the book in regards to weakly or strongly decreasing or increasing approximate sums. How exactly can a sum be weak or strong compared to another?