Answer
$\mathrm{Domain:}\ \ (-\infty,\infty)$
Work Step by Step
Given function: $\quad f(x)=5-2x$
The function will be defined for any value of $\ x\ $. So the domain would be $\ (-\infty,\infty).$
The given function is linear and represents a line. We need at least two points to graph it.
Just pick 2 values of $\ x\ $ and find their corresponding $\ y\ $ values. Then draw the line through those two points.
When $\ x=0,\ y=5-0=5$. So our first point is $\ (0,5)$
When $\ x=2,\ y=5-4=1$. So our first point is $\ (2,1)$
So, here is our graph.