Chapter 5: Linear Systems Section 1: Using Graphs & Tables
Topics in Algebra 1 © 2001, 2002 Texas Instruments Teacher Notes 5-13
Activities (continued)
Enter equations in Y= editor.
Set up the table.
Search for where the
equations are equal.
c. Rewrite the problem in terms of Y1, Y2 and X to prepare to
enter the system into the Y= editor.
Y1 = 12X —or— Y1 = 6X + 48
Y2 = 6X + 48 Y2 = 12X
The independent variable (days at the lake) and the dependent
variable (entry cost) are stated in the problem. Remind
students that the calculator treats X as the independent
variable and Y as the dependent variable.
d. Students need to enter the equations in the Y= editor and
should set up the table. Discuss that the domain of the system
should be whole numbers starting at 0 since x counts the
number of trips to the lake. Notice at x = 8, Y1 = Y2 which is
the breakeven point. If Pat’s family goes to the lake up to and
including 8 times, they might not choose to join the Blue Lake
club.
e. If Pat’s family goes to the lake only 6 times during the summer,
they will spend more money if they join the club for $48.
f. If Pat’s family goes to the lake 10 times during the summer,
they will save money if they join the club. They will save
$120 N $108 = $16. Discuss the savings if the family goes to the
lake more than 10 times. Pose questions such as, when will
they save $50?
Have students find other situations that set fees in this manner.
One source is the national and state park services web pages.
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