Question

How do you find the domain of the function `f(x) = 5/(x-9)`?

Answer 1

The domain is `x!=9`

The nominator of the fraction is not allowed to be `0`, and `x=9` will make it so. All other values are allowed. `x=9` is the vertical asymptote, and `y=0` the horizontal.
graph{5/(x-9) [-3.1, 28.94, -8.96, 7.06]}