Transcript lesson 4.1

4.1 Plot Points in a Coordinate Plane
Warm Up
Lesson Presentation
Lesson Quiz
4.1
Warm-Up
Plot the numbers on a number line.
1. –4, –2, 1, 3
ANSWER
2. –3, 0, 2, 5
ANSWER
3. 0.4, 0.9, 1.3, 1.6
ANSWER
4.1
Example 1
Give the coordinates of the point.
a.
A
b.
B
SOLUTION
a. Point A is 3 units to the left of
the origin and 4 units up. So,
the x-coordinate is –3, and the
y-coordinate is 4. The
coordinates are (–3, 4).
4.1
Example 1
b. Point B is 2 units to the right
of the origin and 3 units down.
So, the x-coordinate is 2, and
the y-coordinate is –3. The
coordinates are (2, –3).
4.1
Guided Practice
1. Use the coordinate plane in
Example 1 to give the coordinates
of points C, D, and E.
ANSWER
C (0, 2), D (3, 1), E (–2, –3)
2. What is the y-coordinate of any point on the x-axis?
ANSWER
0
4.1
Example 2
Plot the point in a coordinate plane. Describe the
location of the point.
a. A(–4, 4)
b. B(3, –2)
c. C(0, –4)
SOLUTION
a.
Begin at the origin. First move 4
units to the left, then 4 units up.
Point A is in Quadrant II.
b.
Begin at the origin. First move 3
units to the right, then 2 units
down. Point B is in Quadrant IV.
Begin at the origin and move
4 units down. Point C is on
the y-axis.
c.
4.1
Guided Practice
Plot the point in a coordinate plane. Describe the
location of the point.
3.
A(2, 5)
ANSWER
4.
Quadrant I
B(–1, 0)
ANSWER
x-axis
4.1
Guided Practice
Plot the point in a coordinate plane. Describe the
location of the point.
5.
C(– 2, –1)
ANSWER
Quadrant III
6.
D(–5, 3)
ANSWER
Quadrant II
4.1
Example 3
Graph the function y = 2x – 1 with domain –2, –1, 0, 1,
and 2. Then identify the range of the function.
SOLUTION
STEP 1
Make a table by substituting the domain values into
the function.
4.1
Example 3
STEP 2
List the ordered pairs:
(–2, –5), (–1, –3), (0, –1), (1, 1),
(2, 3). Then graph the function.
STEP 3
Identify the range. The range consists of the y-values
from the table: –5, –3, –1, 1, and 3.
4.1
Guided Practice
1
7. Graph the function y = – 3 x + 2 with domain –6, –3,
0, 3, and 6. Then identify the range of the function.
ANSWER
range: 0, 1, 2, 3, and 4
4.1
Example 4
VOTING
In 1920 the ratification of the 19th
amendment to the United States
Constitution gave women the right
to vote. The table shows the
number (to the nearest million) of
votes cast in presidential elections
both before and since women were
able to vote.
4.1
Example 4
a.
Explain how you know that the table represents a
function.
b.
Graph the function represented by the table.
c.
Describe any trend in the number of votes cast.
4.1
Example 4
SOLUTION
a. The table represents a function because
each input has exactly one output.
b. To graph the function, let x be the
number of years before or since 1920.
Let y be the number of votes cast (in
millions).
The graph of the function is shown.
4.1
Example 4
SOLUTION
c. In the three election years before
1920, the number of votes cast was
less than 20 million. In 1920, the
number of votes cast was greater
than 20 million. The number of votes
cast continued to increase in the
three election years since 1920.
4.1
Guided Practice
VOTING
8. The presidential election in 1972 was the first election
in which 18-year-olds were allowed to vote. The table
shows the number (to the nearest million) of votes cast in
presidential elections both before and since 1972.
a.
Explain how you know the graph represents a
function.
ANSWER
The table represents a function because each
input has exactly one output.
4.1
b.
Guided Practice
Graph the function represented by the table.
ANSWER
4.1
c.
Guided Practice
Describe any trend in the number of votes cast.
ANSWER
Sample answer: Before 1972, the number of votes cast
increased by 2 million every 4 years. In 1972, the
number increased by 5 million and continued to
increase by more than 2 million every four years since
1972.
4.1
Lesson Quiz
Give the coordinates of the points.
1. A
ANSWER
2. B
1. A(3, 2)
2. B(0, 1)
4.1
Lesson Quiz
Plot the points in a coordinate plane.
3.
A(2, 4)
ANSWER
4.
B(3,0)
4.1
5.
Lesson Quiz
1
Graph y = 2 x – 1 with domain –4, –2, 0, 2, 4. Then
identify the range
ANSWER –4, –3, –2, –1, 0