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1. Holt McDougal Algebra 1
Solving Systems by SubstitutionSolving Systems by Substitution
Holt Algebra 1
Warm UpWarm Up
Lesson PresentationLesson Presentation
Lesson QuizLesson Quiz
Holt McDougal Algebra 1

2. Holt McDougal Algebra 1
Solving Systems by Substitution
Warm Up
Solve the linear equations for x.
1. y = x + 3
2. y = 3x – 4
Simplify each expression.
x = y – 3
2x – 103. 2(x – 5)
4. 12 – 3(x + 1) 9 – 3x

3. Holt McDougal Algebra 1
Solving Systems by Substitution
Warm Up Continued
Evaluate each expression for the given
value of x.
5. x + 8 for x = 6
6. 3(x – 7) for x =10
12
9

4. Holt McDougal Algebra 1
Solving Systems by Substitution
Solve systems of linear equations in two
variables by substitution.
Objective

5. Holt McDougal Algebra 1
Solving Systems by Substitution
Sometimes it is difficult to identify the
exact solution to a system by graphing. In
this case, you can use a method called
substitution.
The goal when using substitution is to
reduce the system to one equation that
has only one variable. Then you can
solve this equation by the methods
taught in Chapter 2.

6. Holt McDougal Algebra 1
Solving Systems by Substitution
Solving Systems of Equations by Substitution
Step 2
Step 3
Step 4
Step 5
Step 1
Pick one equation and solve for one
variable. Circle this equation.
Substitute the resulting expression into the
other equation.
Solve that equation to get the value of the
first variable.
Substitute this value back into the circled
equation from Step 1.
Write the values from steps 3 and 4 as an
ordered pair, (x, y), and check.

7. Holt McDougal Algebra 1
Solving Systems by Substitution
Solve the system by substitution.
Example 1:
y = x + 1
4x + y = 6

8. Holt McDougal Algebra 1
Solving Systems by Substitution
Solve the system by substitution.
Example 2:
x + 2y = –1
x – y = 5

9. Holt McDougal Algebra 1
Solving Systems by Substitution
Example 3:
Solve the system by substitution.
y – x = 3
y = 2x + 5

10. Holt McDougal Algebra 1
Solving Systems by Substitution
Example 4:
Solve the system by substitution.
x = 2y – 4
x + 8y = 16

11. Holt McDougal Algebra 1
Solving Systems by Substitution
Example 5:
Solve the system by substitution.
2x + y = –4
x + y = –7

12. Holt McDougal Algebra 1
Solving Systems by Substitution
Example 6:
y + 6x = 11
3x + 2y = –5
Solve by substitution.

13. Holt McDougal Algebra 1
Solving Systems by Substitution
Example 7:
–2x + y = 8
3x + 2y = 9
Solve by substitution.

14. Holt McDougal Algebra 1
Solving Systems by Substitution
Lesson Quiz: Part I
Solve each system by substitution.
1.
2.
3.
(1, 2)
(–2, –4)
y = 2x
x = 6y – 11
3x – 2y = –1
–3x + y = –1
x – y = 4