Answer
domain: $(-\infty,\infty)$.
range: $(-\infty,\infty)$.
Work Step by Step
$f(x)=4-x$
the function has a zero at x=4
//x<4
f(2)=2
//x>4
f(5)=-1
as f(x) exists for all values of x, the domain and the range is $(-\infty,\infty)$.