Describe how to get the graph of y = √(9 - x) from the graph of y = √x…

Step 1. Reflect. $\sqrt{-x}$ is $\sqrt{x}$ reflected in the y-axis.

Step 2. Move. $\sqrt{-(x - 9)}$ is that moved $9$ to the right.

Step 3. Domain and range. $9 - x \geq 0$ gives the domain $(-\infty, 9]$; the range is $[0, \infty)$.