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