Domain is all of the values of $x$ that give a real answer.
Range is all real values that are possible answers.

You cannot take the square root of a negative number and get a real answer.
What numbers could $x$ be that would make the number under the square root sign negative?
How can you describe what numbers $x$ has to be to get a real answer?

Taking a square root gives a positive number.
There is a negative sign in front of the square root.
What does this tell you about the possible answers?

Domain: $x\le3$
Range: $h(x)\le0$