Answer
$$ \text{Domain: All Real Numbers }$$
Work Step by Step
We see that this function is in the form $ax^2+bx+c$, so it is a quadratic function. Note, the $8$ in the denominator just turns the coefficients into fractions but does not change the form of the function. Since quadratic functions exist for all real numbers, it follows:
$$ \text{Domain: All Real Numbers }$$