1. 1.2 Linear Equations in Two Variables
Writing linear equations

2. How do we define Slope

3. Rise over Run The change of y over the change in x
Given point (x1, y1) and (x2, y2)

4. Find Slope through two points
Lets the points by (6, 10) and (5, -3)
So the slope would be
So the slope is or just 13

5. Slope-intercept form y = mx + b
m is for slope; b is the y intercept
We do we use m for Slope and b for the intercept?
What is the slope of

6. Horizontal lines and Vertical lines
Horizontal line have zero slopes.
Vertical line have undefined slopes.
Why?

7. m =
When (y1) – (y2) = 0, there is no rise in the line. The fraction would equal zero
When (x1) – (x2) = 0, it makes the fraction undefined. The dominator of a fraction can near be zero.

8. What is the difference of a ratio and a rate or rate of change
Ratio have the same units
Rate have different units

9. Writing Linear Equations in 2 variables
Point-Slope form
Lets write equation using the points
(580,50) and (625,47)
The slope would be

10. Using one of the two points
Using the point (580, 50)

11. The General form a line Ax + By + C = 0
A, B and C are not all zero or fractions
Multiply both sides by 15 to get rid of fractions, then add x and subtract 580.

12. Parallel and Perpendicular Lines
Parallel lines have the same slope
Perpendicular line have negative reciprocal slopes

13. Test for Parallel or Perpendicular
Given 2 lines with sets of points
Line1: (0,8) and (4, 5)
Line 2: (6, 10) and (0, 2)
Find the slopes of each line

14. Line 1: has slope
Line 2: have slope
So what are the lines?

15. Homework
Pages 21-24
# 2,8,12,16,22,26,30,34,38,40,46,48,52,56,
60,64,68,72,76,80,84,88

16. Homework
Page 21 – 26
# 13, 25, 41, 51, 79, 89, 101, 107, 117, 123, 134