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6.2 Solving Systems by Substitution
Objectives:
1. Solve systems of linear equations in two variables by substitution.
Example 1: Solve for x when – A. B.
C.
D.
Why is graphing not always the most useful way to solve a system of equations?
We don’t always land on whole numbers!
Remember – when solving a system of linear equations we are looking for an ordered pair that makes both equations true.
We will use substitution when:
1. Both equations are solved for 1 variable.
2. 1 equation is solved for a variable, and one is in standard form.
Example 2: Solve each system by substitution.A. B.
Example 2: continued...
C. D.
Example 3: Josie is deciding between two cell phone plans. The first plan has a $50 sign-up fee and costs $20 a month. The second plan has a $30 sign-up fee and costs $25 a month.
A. After how many months will the total cost be the same?
B. What will the cost be?
C. If Josie has to sign up for a one year contract, which plan would be cheaper?
If both equations are in standard form:
You must solve one of them for a variable and then
substitute.
Example 4: Solve each system by substitution.
A. B.
Trivia1. Which TV show has the characters:Rachel, Ross, Monica, Joey, Chandler, and Phoebe?
2. Which Disney movie has the characters: Prince Eric, Sebastian, Flounder, Ursula, and King Triton?
Little Mermaid
Friends
Example 4: Solve each system by substitution.
C. D.
Practice:
Practice 6.2 WS
Homework
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