Answer:
[tex]x1 = 0 \\ y1 = 0 \\ x2 = 1 \\ y2 = - 3 \\ y - y1 = slop \times (x - x1) \\ y - 0 = \frac{ - 3 - 0}{1 - 0} \times (x - 0) \\ y = - 3x[/tex]