question

These are floor and ceiling symbols, they just round up or down to the nearest integer

So

\( If\;\;f(x)=\lfloor{x}\rfloor\;\;then\;\; f(3.89)=3\\~\\ If\;\;f(x)=\lceil{x}\rceil\;\;then\;\; f(3.89)=4\\\)

thanks for the answer.