## increasing & decreasing functions

Hi, I have two questions regarding increasing & decreasing functions

1. If $x \ge y \Rightarrow f(x) \ge f(y)$, then $f$ is increasing.
So can I say that $f(x)=3$ an increasing function?

2. Suppose I want to find the range of $x$ such that $f(x)$ is increasing, do I solve $f'(x)>0$ or $f'(x)\ge 0$

Thanks!