For a function to be even, it has to meet the following condition:
[tex]f(x)=f(-x)[/tex]To check if the given is an even function, evaluate the function at x and -x:
[tex]\begin{gathered} f(x)=x^2-8 \\ f(-x)=(-x)^2-8=x^2-8 \\ f(x)=f(-x) \end{gathered}[/tex]It means that the function is even.
For a function to be odd, it has to meet this condition:
[tex]f(-x)=-f(x)[/tex]We already know the values of f(-x) and f(x) and from this we can state that the function is not odd.