6.2 Solving Systems by Substitution Objectives: 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: • Both equations are solved for 1 variable. • 1 equation is solved for a variable, and one is in standard form.
Example 2: continued... C. D.
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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. • After how many months will the total cost be the same? • What will the cost be? • If Josie has to sign up for a one year contract, which plan would be cheaper?
Trivia 1. Which TV show has the judges: Mariah Carey, Nicki Minaj, Randy Jackson, & Keith Urban? American Idol 2. Which Disney movie has the characters: Prince Eric, Sebastian, Flounder, Ursula, and King Triton? Little Mermaid
If both equations are in standard form: You must solve one of them for a variable and then substitute.
Practice: • Practice 6.2 WS
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