What is the domain of the real-valued function \(f(x)=\sqrt{x-1}+\sqrt{x-4}\)?

Correct answer: \([4,\infty)\)

For a square root to be real, each radicand must be non-negative. Thus, \(x-1\ge 0\) gives \(x\ge 1\), and \(x-4\ge 0\) gives \(x\ge 4\). The common solution is \(x\ge 4\), so the domain is \([4,\infty)\). Option B considers only the first square root, while option D incorrectly excludes \(x=4\), where both square roots are defined. Exam tip: for multiple square roots, take the intersection of all radicand conditions.