## College Algebra 7th Edition

$\{x|x\neq-3$ and $x\neq 3\}$
We know that $\displaystyle \frac{2x}{x^{2}-9}$ is undefined whenever the denominator is 0, so: $x^2-9=(x+3)(x-3)=0$ $x=3, x=-3$ Thus the domain is: $\{x|x\neq-3$ and $x\neq 3\}$