y = 2√(x + 1) 

Draw the graph: http://www.wolframalpha.com/input/?i=y+%...

Then, draw the horizontal line across that graph at any y-value. That expression is the function since there are no points with same second member. 

To find the domain of the function, we need to know that function exists where.. 

x + 1 ≥ 0 

So we have x ≥ -1 or [-1, ∞) as the domain. 

The range consists of all real values ≥ 0 [Since you can't get negative value from √(x + 1)]. In interval notation, it's [0, ∞) 

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