What is the domain of g(x)=3x^2-6?

Answer 1

Every x-value lies on the graph of this function, so the domain is all reall numbers.

Answer 2

I would say there is no unique answer, as your question is not constrained enough.

Domain of g can be 1, 2, 2.9, any 1 to infinite number of values, including complex numbers, anything that can be properly evaluated in the expression. E.g. if you a matrix subtract a scalar means all elements in the matrix are subtracted by the scalar, then, even matrices can be domain of g.

In other words, domain of a function is part of the definition of the function. E.g. f(x) = |x| be a function? Cannot answer because domain is not defined? If domain is only zero, then yes, it is a function, otherwise not.