Questions from 1.5 HW???
1.6
Graph Using Slope-Intercept
Form
No School Monday: 1/18/10
1.5-1.6 Quiz: 1/22/10
Unit 1 Test: 1/27/10
Vocabulary
 A linear equation of the form
y = mx + b is written in slopeintercept form, where m is the
slope and b is the y-intercept of the
equation’s graph.
y = mx + b
SLOPE
y-intercept
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
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
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?)
Your Turn:
 Identify the slope and y-intercept of
the line with the given equation:
1. Y = -3x + 7
2. Y = 4x – 10
3. 15x – 5y = 10
4. Y = 5 – 7x
Example 2:
 Graph the equation 4x + y = 3 (using
the slope and y-intercept)
Example 3:
 Determine which of the lines are
parallel or perpendicular:




line
line
line
line
a through (-4, 1) and (-6, 7)
b through (-7, -5) and (1, 11)
c through (2, 5) and (4, 9)
d through (4, 3) and (10, 5)
**We need to find
the slope of each
line and then
compare**
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:
Parallel Lines:
have the SAME
slope
Perpendicular
Lines: have
NEGATIVE
RECIPROCALS
as their slopes
Your Turn:
 Graph the
equation
y = 3/4x – 1
Homework:
 P. 32-33 #2-22even, 27-32