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On the Line or Not?

Part of the Graphs & Systems section of Coddy's Algebra journey. Lesson 6 of 61.

Is (4, 5) on the line $y = 2x-3$ ? Can you tell without drawing anything?

Put the x of the point into the rule. Then compare the answer with the y of the point.

For (4, 5): $2\cdot 4-3 = 5$ . This matches the 5, so (4, 5) is on the line.
For (3, 4): $2\cdot 3-3 = 3$ , not 4. So (3, 4) is not on the line.

Challenge

The point (7, $k$ ) lies on the line $y = 3x-5$ . Find $k$ .

Start the lesson to read it in the interactive player and track your progress.

All lessons in Graphs & Systems

1Points and Rules

Two Numbers, One Point A Rule Makes Points The Points Line Up

4Slope-Intercept Form

y = mx + b The Starting Height Write the Equation Solve for y Draw From Any Form Recap: y = mx + b

7Parallel & Perpendicular

Same Slope, Never Meet The Perpendicular Slope A Right-Angle Line Recap: Two Relations

10Systems by Graphing

Two Lines, One Answer Solve by Drawing Check the Crossing When Lines Never Cross Recap: By Graphing

2The Whole Plane

The Four Quadrants Mirror PointsOn the Line or Not?Recap: Rule to Line

5Point-Slope Form

A Point and a Slope From Two Points Flat or Vertical Through Draw From a Point Recap: Point-Slope

8Function Notation

The Name of a Rule Inputs With Signs Find the Input The Graph of f Recap: f(x)

11Solving Systems Exactly

Substitution Isolate First Elimination Scale, Then Add Three Unknowns Two Numbers, Two Facts Recap: Two Methods