Chapter 5: Linear Systems Section 2: Using Algebra
Topics in Algebra 1 © 2001, 2002 Texas Instruments Teacher Notes 5-34
2. Brenda and Cathy can figure out the cost of each top and pair of jeans purchased by the
following.
Let T = price of one top
Let J = price of one pair of jeans
Cathy: 3T + 2J = 57
Brenda: 4T + 3J = 81
To use elimination, multiply Cathy’s equation by 4 and Brenda’s equation by
M
3.
Cathy: 12T + 8J = 228
Brenda: -12T
N
9J =
M
243
Add the two equations to get:
LJ = L15 J = 15
Substitute this value for J into either equation to find T.
3T + 2(15) = 57 3T = 27 T = 9
Interpret the answer:
T = $9.00 per top
J = $15.00 per pair of jeans
Cathy and Brenda paid $9.00 for each top and $15.00 for each pair of jeans.
³ Try-It!é on Your TI.83 Plus and TI.73
Note: The Try-It! exercises cover different functionality available to solve a system of equations. The TI-83 Plus exercise uses the
intersect feature that the TI-73 does not have. The TI-73 exercise uses the Solver to solve an independent system. The TI-83 Plus also has
a Solver feature. Using the Solver feature on the TI-83 Plus is given as a challenge investigation for the students. (Hints are given below.)
The linear system to be solved is the same for both calculators. The problem set, Using Your Calculator to Find Solutions, given after the
Try-It!, is identical and is repeated after each Try-It! for your copying convenience.
On the TI-83 Plus, students will:
• Graph two lines of a system of equations.
• Use r to locate the intersection of the lines.
• Use the y /
intersect feature to find the solution to a system of equations.
Check the solution on the home screen using ¿.
On the TI-73, students will:
• Graph two lines of a system of equations.
• If the lines intersect, use the 1
Solver feature to find the X value of the solution to the
system.
• Find the Y value by using the X on the home screen.
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