The Number System
The Coordinate Plane with Negative Numbers
Plotting points in all four quadrants of the coordinate plane.
Prerequisites
- Absolute Value
All Four Directions at Once
In Grade 5, every point plotted on the coordinate plane sat to the right of and above the origin. But what about a location that's west of a landmark as well as south of it? Before reading on, predict what kind of coordinates such a point would need.
A location west and south of the origin needs negative coordinates in both directions — negative x for west, negative y for south. Extending both axes to include negative numbers divides the coordinate plane into four regions, called quadrants, each with its own consistent pattern of positive and negative coordinates.
Definition — Quadrant
Worked Example — Plotting a Point with Negative Coordinates
Worked Example — Identifying a Quadrant from Coordinates
Graph Visualizer
Domain & range
Evaluate a point
- x^2 = 0
Tip
Common Mistakes
Moving in the wrong direction for a negative coordinate, such as moving right instead of left for a negative x-value.
A negative x-coordinate always means moving left of the origin, and a negative y-coordinate always means moving down — the sign directly controls the direction.
Mixing up which quadrant corresponds to which combination of signs.
Quadrant I is both positive; moving counterclockwise, each quadrant flips one more sign to negative — II flips x, III flips both, IV flips only y.
Key Takeaways
- Extending the coordinate plane with negative numbers creates four quadrants, each with a fixed pattern of coordinate signs.
- The sign of each coordinate directly determines which direction to move from the origin.
- Quadrants are numbered I through IV, counterclockwise starting from the all-positive region.
Summary
The full four-quadrant coordinate plane locates any point in any direction from the origin. The next unit turns from plotting numbers to representing unknown quantities symbolically, beginning with a shorthand for repeated multiplication.
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