excuse me for the quite simple question.
Let us assume that we have the function $f(x)=\frac{a-x}{a}$ where $x \in \mathbb{R} $ and $a$ is a scalar.
I want to mathematically express that the outcome of the function should belong to the set $[0,\infty) $, thus if the outcome is negative is should be changed to zero.
How should the formula be writen?