Day 1

Graphing Linear Equations Using Tables

by Chris Reid

A solution of an equation is the ordered pair (x, y) that makes the equation true for the two variables x and y.

The set of all points (x, y) that are solutions to the equation is the graph of an equation in x and y.

Drections:

Use a table of values to graph the equation.

Process:

Step 1: Rewrite the equation in function form, if necessary.

Step 2: Choose a few values of x and make a table of values.

Step 3: Plot the points from the table. The graph of the equation is the line through theses points.

Example 1:

Use a table of values to graph the equation y = 2x - 1.

 x 2x -1 y Points -1 2(-1)-1 -3 (-1, -3) 0 2(0)-1 -1 (0, -1) 1 2(1)-1 1 (1, 1) 2 2(2)-1 3 (2, 3) Example 2:

Use a table of values to graph the equation 3x + 4y = 8.

First, write in function form.

3x + 4y = 8

4y = -3x + 8

y = -3/4 x + 2

 x -3/4 x + 2 y Points -4 -3/4(-4) + 2 5 (-4, 5) 0 -3/4(0) + 2 2 (0, 2) 4 -3/4(4) + 2 -1 (4, -1) 8 -3/4(8) + 2 -4 (8, -4) Special Graphs:

Example 3:

Graph x = -3.

Each value of x is always -3. Choose different values for y in the table.

 x y Points -3 0 (-3, 0) -3 1 (-3, 1) -3 2 (3, 2) -3 3 (-3. 3) Example 4:

Graph y = 2.

Each value of y is always 2. Choose different values for x in the table.

 x y Points 0 2 (0, 2) 1 2 (1, 2) 2 2 (2, 2) 3 2 (3, 2) Assignment:

Use a table of values to graph each equation.

1. y = x + 1

2. y = -x - 3

3. y = 2x + 1

4. y = -3x + 2

5. 2x - y = 6

6. 3x + 2y = 8

7. x = 4

8. x = -1

9. y = 3

10. y = -2