The domain of a function is the set of values for which the function is defined. So, if you are dealing with a function that contains a square root, you know that the radicand must be non-negative. That is to say:
The solution set of this inequality is the domain of the function.
The range is the set of function values that result from the input of all values of the independent variable in the domain. The smallest value that this function can assume is zero, and it just gets bigger as x gets bigger, so the range is the set of all real numbers greater than or equal to zero.
