1. 3-2 Graphs of Linear Equations in 2 Variables

2. Coordinate Plane y-axis (x,y) Right (+) Up (+) Left (-) Down (-)
origin
x-axis

3. Standard Form Ax + By = C A,B,C are all integers
Any linear equation can be written in this form
Linear equation: Makes a line when graphed
Examples NOT Examples
x + 3y = 9 2x + 3y2 = 6
y = 5 xy = 2
y = 3x – 5

4. Graphing Standard Form
Find the x- and y-intercepts
x-intercept = crosses the x-axis (x,0)
y-intercept = crosses the y-axis (0,y)
Example
x – 2y = 6
x-intercept: x – 2(0) = 6
(6,0)
y-intercept: 0 – 2y = 6
(0,-3)
COVER UP METHOD
Cover up the letter you are not looking for an divide
Must be in STANDARD FORM to use cover-up

5. Graph Continued
(6,0)(0,-3)

6. TOO Graph using intercepts 1) x – y = 3 2) 3x + 2y – 9 = 0 Intercepts:
1) (3,0)(0,-3) 2) (3,0)(0,4.5)

7. Example 2x – 3y = 0 (0,0) (3,2) You need one more point
Pick an x and solve for y
2(3) – 3y = 0
y = 2

8. TOO Graph 1) 2x + 5y = 0 2) x = y Possible Points:
1) (0,0)(5,-2) 2) (0,0)(1,1)

9. Example: One Variable x = 3 Vertical Line y = -2 Horizontal Line
TOO: 2x + 1 = 0
x = -0.5

10. Homework