Lesson 8: Graphing on the Coordinate Plane
The coordinate plane gives every point in 2D space a unique address (x, y). It's the foundation for graphing equations, visualizing data, and understanding geometry.
Key Concepts
The Coordinate Plane
Two perpendicular number lines: x-axis (horizontal) and y-axis (vertical). They meet at the origin (0, 0). A point's address is (x, y): x tells left/right, y tells up/down.
The Four Quadrants
Q1: (+,+) upper right. Q2: (−,+) upper left. Q3: (−,−) lower left. Q4: (+,−) lower right. Points on the axes are not in any quadrant.
Plotting Points
To plot (3, -2): start at origin, move 3 right, then 2 down. To plot (-4, 1): move 4 left, then 1 up. The x-value always comes first in (x, y).
Graphing Linear Equations
To graph y = 2x + 1: make a table of values. x = 0 → y = 1. x = 1 → y = 3. x = -1 → y = -1. Plot the points, connect with a line.
🔬 Interactive Lab: Graphing on the Coordinate Plane Lab
✅ Check Your Understanding
1. What is the ordered pair for a point 3 units right and 4 units down?
2. The point (-2, 5) is in which quadrant?
3. In the ordered pair (x, y), which value controls left and right?