Answer
$y=\sqrt{-x}+9$
Work Step by Step
A radical function that has a domain of all real numbers less than or equal to zero is
$$y=\sqrt{-x}.$$
This function has the range $[0,\infty)$. In order to obtain the range $[9,\infty)$ we add $9$, so the required function is:
$$y=\sqrt{-x}+9.$$
