If you are done:
Take the algebra book from under
your seat.
Begin to read about functions:
Page 46
Writing Functions
September 17, 2014
Can I create equations in two variables to
represent the relationship between two
variables?
You buy a printer for $80 and then
pay $15 for each ink cartridge that
you use. A function relating the
cost, Y (in dollars), of operating the
printer to the number of cartridges
used, x:
Y = 15+ 80.
Let’s talk about the parts of this
function
 Domain: Set of input values
 Range: Set of output values
 Complete the table to represent the total cost for 0
to 4 cartridges.
Number of cartridges
0
1
2
3
4
Total Cost
Graph the function from the table
CHOOSE A REASONABLE SCALE
Let’s analyze this function
 What is the initial value of the cost function? What
does it represent?
 What number of cartridges corresponds to the initial
cost?
 Define the domain.
 Define the range.
 What would the total cost be if you purchased 17
cartridges?
 How would your cost change if the printer cost $90?
Now you try:
Andrea receives a $40 gift card to use a town
pool. It costs her $8 per visit to swim. A function
relating the value of the gift card to the number
of visits.
Write an function to represent this situation.
Make a table of values.
Graph the function
Turn and talk
 What is the initial value? (1 talk to 2)
 What is the difference between a given card value and the
previous card value? (2 talk to 1)
 Identify the domain and the range of the function using set
notation (1 talk to 2)
 Is it possible for the card to have a value of $35? Why or why
not? (2 talk to 1)
On Your Own:
Work on Explore 1 in your groups.
Be ready to share.