# Write Function Rules Using Two Variables

Name
Chapter 9, Lesson 3
Reteach
Date
Write Function Rules Using
Two Variables
CA Standards
AF 1.5, AF 1.1
You will write the rule for the function table.
Rule: ?
Input (a)
Output (b)
2
1
4
2
6
3
8
4
10
5
Step 1 Look at the table carefully. Note that b stands for
the output, and a stands for the input. You are trying to find
the value of b. Begin to write the function rule by placing b
on one side of an equal sign.
b=
Step 2 Look at the first row of the table. Think about how
the input value and the output value are related. There are
two ways to get an output value of 1 when the input value
is 2. One method is subtracting 1 from a. The other method
is dividing a by 2. Since there are two possible choices, you
need to read further in the chart to find a pattern.
Step 3 Repeat the process for the second row. To get an output value of 2 when the
input value is 4, you could subtract 2 from a. The other method is dividing a by 2. Since
dividing a by 2 works for both rows, this is the rule for the function table. Write the rule in
an equation with two variables.
Solution: The rule for this table is b = a &divide; 2.
Write the rule for each function table.
1.
Rule:
2.
Rule:
3.
Rule:
Input (a)
Output (b)
Input (a)
Output (b)
Input (m)
Output (n)
12
11
10
9
8
7
6
5
1
3
5
7
8
10
12
14
24
18
12
6
4
3
2
1
Writing Math Explain how you could write a function rule for
problem 3 using multiplication.
Reteach
Use with text pages 196–198.