A Rule Makes Points
Part of the Graphs & Systems section of Coddy's Algebra journey. Lesson 6 of 64.
An equation with x and y is a rule that turns each value of x into a value of y. Each pair the rule gives you is a point. Take y = x + 2. At x = 0 it gives y = 2. At x = 1 it gives y = 3. At x = 2 it gives y = 4. Three values of x give three points: (0, 2), (1, 3) and (2, 4).
Three points made by y = x + 2
You can choose any value of x, including a negative number. At x = -3 the rule gives y = -1, so (-3, -1) is a point of the rule too. A rule has infinitely many points. A table only shows a few of them.
Challenge
EasyThe rule is y = 2x - 1. Work out y at x = 0 and at x = 2. Then place both points.
Try it yourself
Draw the graph
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Graphs & Systems
1The Coordinate Plane
Two Numbers, One PointThe Four QuadrantsPoints on the AxesMirror PointsRecap: The Plane4Slope-Intercept Form
y = mx + bThe Starting HeightWrite the EquationSolve for yDraw From Any FormRecap: y = mx + b7Parallel & Perpendicular
Same Slope, Never MeetThe Perpendicular SlopeA Right-Angle LineRecap: Two Relations2From Rule to Line
A Rule Makes PointsThe Points Line UpOn the Line or Not?Between the DotsRecap: Rule to Line