Can someone help me figure this out?

Question

Which parent function(s) has/have a domain of all real numbers? There may be more than one correct answer. Select all answers that apply.

 

Cubic, f(x)=x^3

Quadratic, f(x)=x^2

Square root, f(x)=√x

Constant, f(x)=c

Linear, f(x)=x

Answer 1

The domain for four of the functions is all real numbers because you can put in a value of x that is zero, any positive number or any negative number.

 

One of the functions does not have a domain of all real numbers because there are values of x that are not permitted.

 

Based on this information, do you know which one it is?