what is the domain and range for X^2-7

Question

Can someone, anyone answer this asap please it is for my homework and I don't know how to do this and I will be having a test on it.

Answer 1

There is some ambiguity to the question, so I'm going to assume we are just dealing with real numbers.  Given f(x) = x^2-7, the domain is the set of values you can input for x.  In this case, we don't have any restrictions on x, so the domain is (-infinity, infinity). 

 

Now, the range is the set of outputs for our function.  Here, note that x^2>=0.  Thus, the smallest output for f(x) is when x=0.  f(0) = 0^2 - 7 = -7.  Then, notice that as |x| increases, f(x) increases.  Thus the range is [-7, infinity).

Answer 2

Domain :

          Xε ( - ∞ , + ∞) 

 

 

Range:

 

        f( x) ε [ -7 , +∞)

 

  Have to learn how to express domain and range of a function in the appropriate format.