What is the domain of the rational function f(x) = 1/x²-9

1. Identify the denominator of the function:
x^2 - 9

2. Set the denominator not equal to zero:
x^2 - 9 \neq 0

3. Solve for the values of x:
x^2 \neq 9
x \neq \pm 3

4. Combine the results to find the domain:
D(f) = \{ x \in \mathbb{R} \,|\, x \neq 3 \, \text{and} \, x \neq -3 \}

Answer: D(f) = \{ x \in \mathbb{R} \,|\, x \neq 3 \, \text{and} \, x \neq -3 \}