The function f(x)=1/x^2 −9 is not defined at these x values:

Answer 1

f(x) = 1/(x^2-9) = 1/(x-3)(x+3)

the function is undefined at x= 3 or x = -3

UNLESS you really meant

f(x) = (1/x^2) - 9

then it's undefined when x=0