My first math donation in chalk occurred outside of the Helen Matthes Library. Something about Effingham was compelling, and how could I pass up the “Matthes”? So, the project began with a little riff on slope-intercept form.
Many people recall slope-intercept form. Maybe not the name, but folks tend to feel a slight jog in their brain upon mention of y = mx + b. There are two points labeled, though hard to see, in the graph: (0, b) and (1, b + m). (I learned quickly the pale peach color wouldn’t do so well for text.)
The first point is of course the y-intercept arriving on the scene when 0 takes the place of x in the form. Multiple m by 0, add b, and voila y = b when x = 0.
The second point… It’s easy, and I won’t spoil it. You tell me, if you’d like.