The game: get the green function f(x) to pass through the blue points ) and . To reset, click the top-right corner. The function f is controlled by m and b, or rise, run, and b at left. To get more precise values, type them into the input bar at the bottom. For example, you might have to type "m=8/3". The points can be moved by clicking and dragging. They will snap to integer values if close enough. Or, in the input bar, you can type in A=(x, y) for whatever values you like. There are various checkboxes that show or hide information. Have fun! Send me feedback!
Keep somewhere on the y-axis to start, and experiment by moving the other point around. Can you predict when m must be negative? What if the points are horizontal? Vertical?