f(x)=x^2-9
Not sure where to even start...
f(x)=x^2-9
Not sure where to even start...
Recall that the DOMAIN of a function is the set of all possible values of the independent variable (input) in the function that allow the function to work. That is, the domain of a function f(x) is the set of all possible x-values which all the function to work and will thus output real y-values.
f(x) = x^{2} - 9
Note that when finding the domain, if the function contains a fraction the denominator of the fraction cannot equal 0. Also, the values under a square root sign must be positive (since the square root of a negative number yields an imaginary number).
These criteria, however, are not applicable for the function in question since it does not contain a fraction or a square root.
Thus, the domain for this function is
all real numbers ==> { x ¦ all real numbers x } ==> (-∞, ∞)