f(x)=18-21x+3x^3 what is the domain and the range

domain is all values x can be. Since you are not dividing by x you don't really need to worry about it because in your case x can be any number. Therefore the domain is xeR which stands for any number

Well, xeR is any non-imaginary number :)

The range is the values of f(x) that you can get out, in this case it is an odd function, so likewise the range is x E R

(by e or E we mean the curly E which means "is an element of")

Capuchin range is y E R not x E R.

well, f(x) E R :)

usually people don't write it like this but yes you can do that. Although you did say x E R :)

The domain and range are both equal to the set of real numbers.