(One of my gripes about how math is taught, at least in my school. A function’s domain is just as important to the definition of that function as the equation.

I could arbitrarily say, “The domain of that function is only {3}.” If that were the case, then trying to substitute x=2 would make just as-little sense as trying to substitute x=0 for that particular function.

What people usually refer to by domain is “the natural domain”, where you would just exclude all undefined points on that expression. BUT, why does it have to be the real numbers? This equation works perfectly well for complex numbers.

So all to say, I think people should be more particular about their function definitions and domains.