f(x) = - 55x + 330
The domain is the set of possible input-values, i.e. x-values.
You know that f(x) cannot bebigger than 330 not lower than zero, then construct the inequality:
0 ≤ f(x) ≤ 330
0 ≤ - 55x + 330 ≤ 330
Multilply by - 1 and change the inequality signs:
0 ≥ 55x - 330 ≥ -330
Add 330 to all the members
330 ≥ 55x ≥ 0
Divide by 55
6 ≥ x ≥ 0 => 0 ≤ x ≤ 6
The the possible x-values (practical domain) is all the real numbers between 0 and 6 inclusive.
