Question

Why is domain (input) and range (output) important when defining a function?

Answer 1

In its simplest form the domain is all the values that go into a function, and the range is all the values that come out. But in fact they are very important in defining a function.

Answer 2

The domain is all the values that go into a function. The range is all the values that come out. They’re important because without the domain you would have to assume that f (x) is everywhere which would be false.