Answer
See graph and explanations.
Work Step by Step
Step 1. Graph the function $f(x)=\sqrt x$, shown as the blue curve in the figure.
Step 2. To obtain the graph of function $g(x)=\sqrt {3-x}=\sqrt {-(x-3)}$, shift the original horizontally 3 units to the right, then reflect the result around $x=3$ (shown as the red curve in the figure).