1) As the Domain is the set of inputs (x) for that function, as we can see in the graph.
There's one point in the graph x =8, where should be an asymptote i.e. a vertical or horizontal line that prevents both graphs do not trespass.
So we can write the Domain as
D =(-∞, 8) U (8, ∞)
Because in this function, the point x=8 is not included, and from point 8 on the function continues.