Answer
Always
Work Step by Step
The reason why any equation with a form of y=kx will always pass through the origin (0,0) because no matter what k is, when you plug in 0 for both x and y, you will get 0=0 which is always true. You can also look at graphically. There is no vertical transformation with the graph but only a horizontal or vertical compression depending on k so the only thing the line can change is by how steep it gets. The graph can never go up or down so it has to pass through the origin.
