f(x) = (x-2)/(x-4)

g(x) = 3/(x-5)

find the domain

f(x) = \frac {(x-2)}{(x-4)}

g(x) = \frac 3{(x-5)}


For the first one, the domain is (-infinity , 4) U (4 , +infinity) (all real numbers except 4)
For the second one, the domain is (-infinity , 5) U (5 , +infinity) (all real numbers except 5)

do you understand why 4 and 5, respectively, are not included in the domain? It's simply because dividing by zero is not defined.