Question

What are the restrictions of the domain of the function F(x) = 1/x^2-9

Answer 1

$f(x)=\frac{1}{x^2-9}$

The denominator can't be equal to 0.
$x^2-9 \not= 0 \\ x^2 \not= 9 \\ x \not= -3 \ \land \ x \not= 3$

The domain is all numbers except -3 and 3.
$x \in \mathbb{R} - \{-3, 3 \}$