Find Domain of Function?

Question

I am not sure if this is a hard problem but I am unable to find anywhere in my book how to do this problem

f(x)=(1/2)x-5
4
The domain of f^-1 is the interval [A,B]

Please Help!!!

Answer 1

The domain of f^-1 is the range of f.
If 4 ≤ x ≤ 5
then 2 ≤ (1/2)x ≤ 5/2
and -3 ≤ (1/2)x - 5 ≤ -5/2
So the range of f is [-3, -5/2] and this is also the domain of f^-1.