You mean ?

Only non-negative numbers can be under the square root, so solving the inequality would give us the values of x we want. Solving the corresponding equation would give use the critical values of 0 and 3. Now test different values of x to see if what's underneath the square root is non-negative.

For , , check.

For , , check.

For , , NOPE.

For , , check.

For , , check.

So our domain is .

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