Find the domain of the function \(f(x)=\sqrt{x^2-16}\).

Correct answer: \(( -\infty,-4]\cup[4,\infty)\)

For a real square root, the expression inside the radical must be non-negative. Hence, \(x^2-16\geq 0\), or \((x-4)(x+4)\geq 0\). This inequality holds when \(x\leq -4\) or \(x\geq 4\). Therefore, the domain is \(( -\infty,-4]\cup[4,\infty)\). Options B and C contain values between the roots, for which \(x^2-16<0\). Option D is incorrect because at \(x=-4\) and \(x=4\), the square root is 0. Exam tip: For a real square-root function, set the radicand greater than or equal to zero.