Answer:
--- quadratic function
--- linear function
--- square root function
Step-by-step explanation:
Given
The attached graph
Required
The domain of each function
Starting from the left; the first function is the quadratic function.
The curve of the quadratic function stops at -2 So, the domain is:

The straight line that starts at -2 and ends at 6 is a linear function.
So, the domain is:

Lastly, the square root function begins at 6. So, the domain is:
