If the real function (f(x)=\frac{\sqrt{x-2}}{x^2-9}) is given, what is its domain?

Correct answer: ([2,\infty)-{3})

For the square root (x\ge 2), and for the denominator (x\ne -3,3) are required. But (-3) is already outside (x\ge 2), so only (3) is removed.