You don't "add the 5" in any event. Multiplication is very different from addition, and precision of vocabulary is important.
It depends on what your teacher or answer key expect. You can take a hint from the fact that the given polynomials are all multiplied out.
(5x^2 +5)/(x -1)
_____
The domain of polynomials in general is "all real numbers." However, you must exclude any specific numbers that make the rational expression be undefined. This includes numbers that make the denominator of the numerator zero, as well as those that make either the numerator or the denominator of the denominator zero. In other words, you must exclude from the domain
.. x ∈ {-5, 1, 2}
