Download Lesson 1.3 Represent Functions as Graphs

Lesson 1-3, 1-4
Represent Functions as Graphs;
Graphing Linear Equations using
Intercepts.
Graph a function
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Graph the function y=3x with domain
0,1,2,3,4.
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Step 1: Make an input-output table.
X
0
1
2
3
4
y
0
3
6
9
12
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Step 2: Plot a point for each ordered pair.
Practice Problems
Graph the functions:
 1) y=2x+3
Domain: 0,2,4,6,8
 2) y=-2x-7
Domain: 1,2,3,4,5
 3) y=-3/4x+6
Domain: 0,4,8,12,16
 4) y= y=1/2x-4
Domain: 1,2,3,4,5
 5) y=1/3x-3
Domain: 0,3,6,9,12
Write a function rule for a
graph.
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See Graph
Step 1: Make a table
Step 2: Find a relationship between the
inputs and outputs.
Step 3: Write a function rule.
Helpful Hints to Writing Rules
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First, check for a common DIFFERENCE
between x and y values.
For example,
x
1
3
4
7
y
3
5
6
9
•The DIFFERENCE of every value of x and y is
2. Therefore, the rule is y=x+2.
Helpful Hints to Writing Rules
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Second, if no common difference is found,
check for a COMMON MULTIPLIER.
For example,
x
1
2
3
4
y
4
8
12
16
•Every value of x can be multiplied by 4 to get
the values for y. Therefore, the rule is y=4x.
Helpful Hints for Writing Rules
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If no common difference or multiplier can be
found, check for BOTH!
For example,
x
1
2
3
4
y
4
7
10
13
•In the table above, there is no common difference between x and
y. 4-1=3 but 7-2=5. Also, there is no common multiplier. 1x4=4, but
2x4≠7. Therefore, we check for BOTH, 1x3=3, then, 3+1=4.
3x3=9, then, 9+1=10. So, the rule is y=3x+1.
Lesson 1-4 Graph Using
Intercepts
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Find x-intercept and y-intercept of the graph of 7x3y=21
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Solution: To find x-intercept, sub 0 for y and solve for x.
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7x-3y=21
7x-3(0)=21
x=21/7 or x=3
To find y-intercept, sub 0 for x and solve for y.
7x-3y=21
7(0)-3y=21
y=-21/3 or -7
Use a Graph to find Intercepts
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Find the x and y intercepts of the
graph.
(2,0)
(0,-4)
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The line crosses the x-axis at 2, therefore the x-intercept is 2. The line
crosses the y-axis at -4, therefore the y-intercept is -4.
Use Intercepts to Graph an
Equation
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Graph 3x+2y=6. Label the points where the line
crossed the axes.
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Step 1: Find the intercepts.
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x-intercept
3x+2y=6
3(0)+2y=6
y=3
y-intercept
Step 2: Plot the points on a graph.
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3x+2y=6
3x+2(0)=6
x=2
X-int= (2,0)
Y-int= (0,3)
Step 3: Connect the points with
a line.
(0,3)
(2,0)
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Guided Practice
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Pg. 18 Problems 1-5
Assignment pg. 19 1-27 (odd only)