WarmUp

1
Warm-Up
6 minutes
Solve for y.

• 4x y 3
• x 2y 10
• -3 6y 2x
• Graph the points A(2,5), B(3,7), and C(5,11).
  Connect the points with a line. Estimate where
  the line crosses the y-axis.

2
1.2 Slopes and Intercepts

• Objectives
• Graph a linear equation
• Write a linear equation for a given line in the
  coordinate plane

3
Slope of a Line
run
rise
4
Example 1
Find the slope of the line containing points
(1,6) and (5,4).
5
Slope-Intercept Form
Find the slope of the line y 2x - 4.
8
y 2x - 4
6
4
2
-4
0
6
8
-2
1
-8
-6
-4
-2
4
2
-2
rise -4
0
2
-4
run -2
-6
-8
The y-intercept is -4.
6
Slope-Intercept Form
y mx b
y 4x 8
y 2x - 3
slope
y-intercept
slope
y-intercept
4
8
slope
y-intercept
2
-3
7
Example 2
Graph 3x 4y 12.
3x 4y 12
solve for y
-3x -3x
4y 12 3x
4
4
8
Example 2
Graph 3x 4y 12.
8
6
4
2
6
8
-8
-6
-4
-2
4
2
-2
-4
slope
-6
y-intercept
-8
9
Standard Form
The standard form of a linear equation in two
variables is Ax By C, where A,B, and C are
constants and A and B are not both 0.
3x 4y 12
6x 7y 23
10
Example 3
Graph 2x 5y 10 using intercepts.
To find the y-intercept, let x 0.
2x 5y 10
2(0) 5y 10
0
2
0 5y 10
5y 10
5
5
y 2
11
Example 3
Graph 2x 5y 10 using intercepts.
To find the x-intercept, let y 0.
2x 5y 10
2x 5(0) 10
0
2
2x 0 10
5
0
2x 10
2
2
x 5
12
Example 3
Graph 2x 5y 10 using intercepts.
8
6
4
2
2
0
6
8
-8
-6
-4
-2
4
2
0
5
-2
-4
-6
-8
13
Example 4
Graph y -2.
write the equation in standard form
Ax By C
(0)x (1)y -2
for any value of x
y -2
14
Example 5
Graph x 7.
write the equation in standard form
Ax By C
(1)x (0)y 7
x 7
for any value of y
15
Homework
p.17 13,17,21,25,29,35,37,39,41,47,53,59