21.1.1 A Refresher: Watching One Variable Move with Another
21.1 From Coordinates to Direct Proportion: The Plainest Kind of Change
Point 1 of 5
21.1.1 A Refresher: Watching One Variable Move with Another
Core idea
Walk a point across the grid paper once more and feel again that "fix one quantity and the other is settled" — that's exactly what a function y=f(x) means.
Module goal. Building on the coordinate plane and the idea of a function, meet the simplest family of functions — direct-proportion functions — and lock in the core picture: a graph that's a straight line through the origin.
eastmath.com · 21.1 From Coordinates to Direct Proportion: The Plainest Kind of Change · 21.1.1 A Refresher: Watching One Variable Move with Another