Question 36489
I see a lot of questions like this here.  There must be some sort of misunderstanding of the definition of a function floating around schools.
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First, the domain and range of a function are defining properties of that function.  So when you write down a formula you, strictly speaking have not told me the function you are talking about until you specify a domain. 
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So this sort of question is badly worded.  What you mean to ask is:  "For what real number arguments is this function undefined?"
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In which case the answer is that your function is not defined for x<2.
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Once you know the domain, (and only then) you can talk about the function's range.  You know that the (principle) sqrt function assumes all positive values of x for arguments greater than or equal to 0, so this function of yours will have also have a range of all positive real numbers.