The area under the square root sign, called the radicand, must be positive or zero for real numbers ℝ. So, that means that x must be positive or zero. Written algebraically, [tex]x \geq 0[/tex]. The question seems to want you to really show that x can be any number between zero and infinity, so we can write a compound inequality [tex]0 \leq x\ \textless \ \infty[/tex].
