The Name of a Rule
Part of the Graphs & Systems section of Coddy's Algebra journey. Lesson 37 of 64.
Rules get names. f(x) = 2x + 1 names the rule "double, then add one" f, and f(3) means "f applied to 3": substitute 3 for x and compute.
f(3) = 2(3) + 1 = 7
The notation reads "f of 3", and it is a value, not a multiplication: f(3) is what the rule gives back, the y that belongs to x = 3.
Named rules can coexist: f(x) = 2x + 1 and g(x) = x - 4 are two machines on one desk, and f(3) and g(3) are their separate outputs for the same input.
Challenge
The rule is g(x) = 3x - 2. Work out g(4).
Try it yourself
Simplify the expression
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