Question

What is the domain of g(x)=1-2x^2

Answer 1

The domain of this expression is all real numbers except where the expression is unidentified. In this case, there is no real number that makes this expression unidentified.

Answer 2

The domain is the set of all numbers that can be used such that when used, the function is defined

sometimes numbers that are restricted or make it undefined are values that make division by 0 or sqrt of a negative

we see that there is none of that going to happen so domain is all real numbers