1. Algebra 1
Section 5.1

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3. Definitions
An ordered pair is a pair of numbers (x, y) describing a point in the Cartesian coordinate plane.
The two symbols in an ordered pair are called coordinates.

4. Quadrants
The perpendicular number lines divide the Cartesian coordinate plane into four sections called quadrants. II I
III IV

5. Definitions The x-axis is the horizontal number line in the plane.
The y-axis is the vertical number line in the plane.
The origin is the point (0, 0), where the axes intersect.

6. Plotting Points
In the Cartesian plane, the horizontal distance (x) always comes first and the vertical distance (y) second.
An ordered pair with unknown coordinates is usually expressed (x, y).

7. Definitions
The x-coordinate (abscissa) is the first coordinate of an ordered pair.
The y-coordinate (ordinate) is the second coordinate of an ordered pair.

8. Example 1 y
a. (2, 1)
b. (-3, 4)
c. (0, -5)
(-3, 4)
(2, 1) x
(0, -5)

9. Plotting Points (x, y) Move x units right or left from the origin.
From that position, move y units up or down.
Graph the point and label it with its coordinates.

10. Example 2 E (-3, 5) Quad. II D (-1, -2) Quad. III F (4, 0) On x-axis y

11. Definition
A scatterplot is a graph on a Cartesian plane that summarizes the relationship between two sets of numbers.

12. Example 3
Adjust the scale of the axes and their intersection to fit the data.
Plot the ordered pairs.

13. Example 3 In general, as height increases, so does weight.
The graph rises from left to right.

14. Homework: pp