Hi, I have two questions regarding increasing & decreasing functions

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

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