You should remember that the domain of the function consists of all values that make the function to exist, hence, in the provided case, the function ceases to exist for `x=5`  and `x=-3` , hence, these two values needs to be excluded from domain of definition.

Domain = `R - {-3 , 5}`

You may use the interval notation to write the domain of the function such that:

`(-oo,-3)U(-3,5)U(5,+oo)`  (the symbol "U" represents the union)

Hence, using the interval notation to write the domain of the function that is not defined at `x=-3`  and `x=5`  , yields `(-oo,-3)U(-3,5)U(5,+oo).`