# 5.1: Points & Lines & Slopes

**At Grade**Created by: CK-12

*This activity is intended to supplement Algebra I, Chapter 4, Lesson 3.*

## Problem 1 – Coordinates of Points

Open the *CabriJr* app by pressing **APPS**. Open a new file and make sure the axes are displayed. Place a point,

1. Explain what is common to all points on the

2. Explain what is common to all points on the

Delete points

Complete the sentences by writing *positive* or *negative*.

3. A point is in Quadrant 1 (top right) when its

4. A point is in Quadrant 2 (top left) when its

5. A point is in Quadrant 3 (bottom left) when its

6. A point is in Quadrant 4 (bottom right) when its

Draw two lines through point

7. What is this relationship between the coordinates of point

## Problem 2 – Lines, Equations, and Slopes

Delete or hide the segments and measurements. Draw a line connecting

Look for relationships between the slope and equation as you change the line by grabbing and dragging point

8. When dragging the line by point

9. When dragging the line itself, what is changing in the equation?

10. Drag point

## Problem 3 – Slopes of Parallel and Perpendicular Lines

Open the Cabri Jr. file **PARALLEL**. Drag the lines by points

11. What can you say about the slopes of two parallel lines?

Open the Cabri Jr. file **PERPENDI**. Again drag the lines to investigate the relationship between the slopes.

12. What can you say about the slopes of two perpendicular lines?

Use the **Calculate** tool to see what happens when the slopes of two perpendicular lines are multiplied together. Select one slope measurement, press

Now, change the lines by grabbing and dragging point

13. What do you observe about the product of the slopes?