Embed Size (px)
Citation preview
4.3 – QUICK GRAPHS USING INTERCEPTS
Algebra 1(A/B)Fall 2012
Today’s Schedule
Class Announcements Homework Check Warm-Up 4.3 Notes Begin Homework
Homework Check Compare your answers with the
person next to you. This is not chat time!
Ask about questions that you are not sure about. Correct those questions in class. Study from those questions!
Warm-Up Look at the ordered pair on
your desk. This ordered pair represents
your location on a coordinate plane.
Stand up if your point matches the following descriptions.
You will need scratch paper!
Stand up if…
you are in Quadrant III.
Stand up if…
you are on the x-axis.
Stand up if…
you are in Quadrant I.
Stand up if…
you are the origin.
Stand up if…
you are in Quadrant IV.
Stand up if…
you are on the y-axis.
Stand up if…
you are in Quadrant II.
Stand up if…
you are a solution to the equation 3y = 3x + 3.
(0, 1), (-1, 0), (-2, -1), and (-3, -2)
Stand up if…
you are on the line y = -2.
Stand up if…
you are a solution to the equation 4x + 2y = 6.
(1, 1) and (2, -1)
Stand up if…
you are on the line y = 1.
Stand up if…
you are a solution to the equation 6y = -12 + 6x.
(0, -2), (1, -1), (2, 0), and (3, 1)
Stand up if…
you are on the line x = -4.
4.3 - Quick Graphs Using Intercepts
Objectives: Find the intercepts of a graph of
a linear equation.
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
y = 4
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2x = -6
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
y = -1
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
x = 2
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
y = 0
How many points does it take to determine a line?
We need at least two points to determine a line.
Why do we need at least two points?
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
Intercepts
x-intercept – the point where a line or curve crosses the x-axis. This is always written as (x, 0).
y-intercept – the point where a line or curve crosses the y-axis. This is always written as (0, y).
Intercepts
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
x-intercept?
y-intercept?
(0, 3)y = 3
(2, 0)x = 2
Intercepts
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
x-intercept?
y-intercept?
(0, -3)y = -3
(6, 0)x = 6
Break Time Use this time to relax or try the
following rebus puzzles.
All over again You are up in arms over it
What if we are not given a graph? How do we determine the x and y-intercepts?
We can find the… x-intercept by setting y = 0
y-intercept by setting x = 0
Find the x-intercept and y-intercept of the graph of the following equation.
To find the x-intercept, set y = 0 and solve for x.
To find the y-intercept, set x = 0 and solve for y.
2x + 3y = 6
We can make a line given our two intercepts!
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
(3, 0) and (0, 2)
Find the x-intercept and y-intercept. Then graph the line. 1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
2x – y = 4
Find the x-intercept and y-intercept. Then graph the line. 1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
y – 2x = 3
Find the x-intercept and y-intercept. Then graph the line. 1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
y = 2x + 4
Find the x-intercept and y-intercept (if possible). Then graph the line.
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
2y – 3 = 5 Variable x does not
show up no x-intercept!
Graph and write the equation of the horizontal line passing through (3, -4) and (-6, -4).
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
Graph and write the equation of the vertical line passing through (3, 2) and (3, -5).
1
2
3
5
6
4
7
-6
-2
-4
1 2 3 4 5 6 7-6 -4 -2
Recap:1. The x-intercept and y-intercept are
the points at which a line or curve cross the x and y-axis, respectively.
2. To find the x-intercept, set y = 0.3. To find the y-intercept, set x = 0.4. We can graph a line by connecting
the two intercepts.
Homework: pgs. 221-222 #14-19, 26-28, 35-37, 44-46
