Check the Crossing
Part of the Graphs & Systems section of Coddy's Algebra journey. Lesson 49 of 64.
A crossing read off a drawing deserves a check: substitute it into BOTH equations. For the system y = x + 2 and y = 3x - 2, the point (2, 4) checks as 4 = 4 and 4 = 4: solved. A point that satisfies one line but not the other is on one line only, not a solution of the system.
The check is also how a crossing can be found without a full drawing: where the lines meet, their right sides agree, so x + 2 = 3x - 2, a one-variable equation whose solution is the crossing x.
Challenge
The lines y = x + 5 and y = 2x + 1 cross at one point. Find its x and y.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
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 Relations10Systems by Graphing
Two Lines, One AnswerSolve by DrawingCheck the CrossingWhen Lines Never CrossRecap: By Graphing2From Rule to Line
A Rule Makes PointsThe Points Line UpOn the Line or Not?Between the DotsRecap: Rule to Line