Question

State the domain and range and determine if it's a function?

Answer 1

if we do a vertical line test on that graph, we'll find that a vertical line will pass by and hit the line only once on its way down, only once meaning the graph is the graph of a function.

Range

well, is really how high and low it goes or namely over the y-axis.

well, it goes up up up to 3 then U-turns and back down it goes, now the graph has arrowheads, meaning the graph keeps on going towards infinity, vertically as well as horizontally since it's a parabola, so the range will be

[3 , +∞)

Domain

well, is simply how left and right it goes or namely over the x-axis.

judging from the arrowheads it moves from infinity to infinity, so

(-∞ , +∞).