You need to picture the graph its a parabola and curves from left to right outward forever the x values on a graph are from left to right and are the domain of a function.
The range is all of the y values (up and down) This will change depending on where your vertex is ( the bottom of your graph). You'll need to find the vertex. There is a handy formula to find the axis of symmetry x= -b/2a This is the line that runs down the middle of your parabola. When you find x, substitute it into the parabola to solve for y. That will be your lowest point if your parabola is positive. Since yours doesn't' have a b value the axis of symmetry is 0. and your vertex would be 4. so (0,4) is your lowest point. Since its your lowest point and your parabola is pointing up all of your y values (your range, remember?) will be above this including 4 don't forget that. so your range is y≥ 4.
