I'd really appreciate it if anyone could ! : ) which graph represents the piecewise function?

The upper right corner choice

The idea is that you graph y = x+3 but only when x < 0 (which is everything to the left of the y axis). This line goes through (-3,0) and (0,3). Note the open hole at x = 0 to indicate "do not include this point"

At the same time, you will also graph y = 2x but only if x is 0 or larger. The endpoint here is (0,0) which is a closed circle telling us to include this endpoint. Another point on this line is (1,2).

go hook jvc hgv cj xk jvc 6756