Notes Over 4.8
Identifying Functions
Function
A relation where each input has
exactly one output.
Decide whether the relation is a function. If it is a function,
give the domain and the range.
1. Input
Output
2
1
4
3
5
8
7
Not a function, because 4
goes to both 3 and 5
Notes Over 4.8
Identifying Functions
Function
A relation where each input has
exactly one output.
Decide whether the relation is a function. If it is a function,
give the domain and the range.
2. Input
Output
Domain: the input
Range: the output
1
1
2
4
3
9
4
16
A function, because every
input goes to only one output
D  1, 2, 3, 4 
R  1, 4, 9, 16
Notes Over 4.8
Identifying Functions
Function
A relation where each input has
exactly one output.
Decide whether the relation is a function. If it is a function,
give the domain and the range.
3. Input
Output
Domain: the input
Range: the output
1
2
4
3
6
4
8
A function, because every
input goes to only one output
D 1, 2, 3, 4
R   4, 6, 8

Notes Over 4.8
Identifying Functions
Function The equation y = 3x – 4 becomes f(x) = 3x – 4,
Notation where the solution (x, y) becomes (x, f(x)).
Evaluate the function when x = 3, x = 0, x = - 2.
4. f  x   9 x  2
f 3  93  2  27  2  29
f 0  90  2  0  2  2
f  2  9 2  2  18  2  16
Notes Over 4.8
Identifying Functions
Function The equation y = 3x – 4 becomes f(x) = 3x – 4,
Notation where the solution (x, y) becomes (x, f(x)).
Evaluate the function when x = 3, x = 0, x = - 2.
5. f  x   0.5 x  4
f 3  0.53  4  15
.  4  55
.
f 0   0.50   4  0  4  4
f  2   0.5 2  4  1  4  3
Notes Over 4.8
Identifying Functions
Function The equation y = 3x – 4 becomes f(x) = 3x – 4,
Notation where the solution (x, y) becomes (x, f(x)).
Evaluate the function when x = 3, x = 0, x = - 2.
6. f  x   7 x  3
f 3  73  3  21  3  18
f 0   70   3  0  3  3
f  2   7 2   3  14  3  17
Notes Over 4.8
Writing and Using a Linear Function
7. While on vacation, your family traveled 2040 miles
in 6 days. Your average speed was 340 miles per day.
a. Write a linear function that models the distance
that your family traveled each day.
Verbal
Distance
Average
Time


Model
traveled
speed
Labels: Distance traveled
=f(t)
Average speed
= 340 miles per day
Time
= t days
f t   340t
Notes Over 4.8
Writing and Using a Linear Function
7. While on vacation, your family traveled 2040 miles
in 6 days. Your average speed was 340 miles per day.
b. Use the model to find the distance traveled after
1.5 days of travel.
f t   340t
f 1.5  3401.5
f 1.5  510
Notes Over 4.8
Writing and Using a Linear Function
7. While on vacation, your family traveled 2660 miles
in 7 days. Your average speed was 380 miles per day.
a. Write a linear function that models the distance
that your family traveled each day.
Verbal
Distance
Average
Time


Model
traveled
speed
Labels: Distance traveled
=f(t)
Average speed
= 380 miles per day
Time
= t days
f t   380t
Notes Over 4.8
Writing and Using a Linear Function
7. While on vacation, your family traveled 2660 miles
in 7 days. Your average speed was 380 miles per day.
b. Use the model to find the distance traveled after
1.5 days of travel.
f t   380t
f 1.5  3801.5
f 1.5  570
Notes Over 4.8