1. Questions from 1.5 HW???

2. 1.6 Graph Using Slope-Intercept Form
No School Monday: 1/18/10
Quiz: 1/22/10
Unit 1 Test: 1/27/10

3. Vocabulary
A linear equation of the form y = mx + b is written in slope-intercept form, where m is the slope and b is the y-intercept of the equation’s graph.
y = mx + b
SLOPE
y-intercept

4. Both lines have a slope of 3. So the lines are PARALLEL
Vocabulary
Two lines are parallel if the do NOT intersect.
Parallel lines have the SAME slope.
Ex: y = 3x – 2 and y = 3x + 5
Both lines have a slope of 3. So the lines are PARALLEL

5. What is a negative reciprocal??
Vocabulary
What is a negative reciprocal??
Two lines are perpendicular if they intersect to form a right angle.
Perpendicular lines have slopes that are negative reciprocals.
Ex: y = 2x – 3 and y = -1/2x -7
2 and -1/2 are negative reciprocals. So the lines are PERPENDICULAR

6. Example 1:
Identify the slope and y-intercept of the line with the given equation.
Y = 1/4x – 2
-2x + 3y = 9
(what do we need to do to this equation before we can
identify slope and the y-intercept?)

7. Your Turn:
Identify the slope and y-intercept of the line with the given equation:
Y = -3x + 7
Y = 4x – 10
15x – 5y = 10
Y = 5 – 7x

8. Example 2:
Graph the equation 4x + y = 3 (using the slope and y-intercept)

9. **We need to find the slope of each line and then compare**
Example 3:
Determine which of the lines are parallel or perpendicular:
line a through (-4, 1) and (-6, 7)
line b through (-7, -5) and (1, 11)
line c through (2, 5) and (4, 9)
line d through (4, 3) and (10, 5)
**We need to find the slope of each line and then compare**

10. Example 3 continued: Find the slope of line a:
Parallel Lines: have the SAME slope
Perpendicular Lines: have NEGATIVE RECIPROCALS as their slopes
Example 3 continued:
Find the slope of line a:
Find the slope of line b:
Find the slope of line c:
Find the slope of line d:

11. Your Turn:
Graph the
equation
y = 3/4x – 1

12. Homework:
P #2-22even, 27-32