Flat or Vertical Through
Part of the Graphs & Systems section of Coddy's Algebra journey. Lesson 25 of 64.
Through any one point there is only one flat line and only one vertical line. You can write both equations straight from the point. The flat line through (2, 5) has every point at height 5, so its equation is y = 5. The vertical line through (2, 5) has every point at x-coordinate 2, so its equation is x = 2.
The flat and the vertical line through (2, 5)
Point-slope form also works for the flat line, because its slope is 0. Substituting m = 0 and the point (2, 5) gives y - 5 = 0(x - 2). The right side is 0, so y = 5. Point-slope form cannot give the vertical line, because a vertical line has no slope to substitute. Write its equation directly as x = 2.
Challenge
MediumDraw the flat line through the point (4, -3).
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 Relations2From Rule to Line
A Rule Makes PointsThe Points Line UpOn the Line or Not?Between the DotsRecap: Rule to Line5Point-Slope Form
A Point and a SlopeFrom Two PointsFlat or Vertical ThroughDraw From a PointRecap: Point-Slope