The Name of a Rule
Part of the Graphs & Systems section of Coddy's Algebra journey. Lesson 37 of 64.
A rule can be given a name. Function notation writes f(x) = 2x + 1 to name the rule "double, then add 1" as f. Then f(3) means the rule f applied to the input 3. To work it out, substitute 3 for x and compute:
f(3) = 2(3) + 1 = 7
You read f(3) as "f of 3". It is a value, not a multiplication. f(3) is the output the rule gives for the input 3, the y that belongs to x = 3.
Different rules get different names. Take f(x) = 2x + 1 and g(x) = x - 4. The same input 3 gives f(3) = 7 and g(3) = -1. Each function uses its own rule.
Challenge
MediumThe 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