You would have to plug in x as 0, and you would get y=-2(0)+4=4, and since this will keep decreasing as you decrease from 0, the range of the function is y < 4.
To graph it, you would choose some x-values (let's use 0, -1, -2) and then plug them in. y= -2(0)+4=4, y=-2(-1)+4=2+4=6, and y=-2(-2)+4=4+4=8, so the coordinates are (0,4), (-1,6), (-2,8). Just graph these and connect them with a line.
