1. 3.2 + 3.3 kids notes Substitution.notebook September 11, 2012
Objective ­ solve systems using substitution and elimination
Agenda
1. WU
2. Check HW Warm Up
3. Notes
4. HW
Simplify
­(4x ­ 5) + 2(x + 6)
SUBSTITUTION This method works well when a variable is already by itself.
1. x = 2y + 5
4x + 3y = 9
Steps:
1. Solve
2. Substitute
3. Solve
4. Substitute
1

2. 3.2 + 3.3 kids notes Substitution.notebook September 11, 2012
2. y = 2x
4x ­ y = 6
3. 3x + 2y = 7
x ­ 2y = ­3
2

3. 3.2 + 3.3 kids notes Substitution.notebook September 11, 2012
4.
Equations: 3x ­ y = 5
4x + 2y = 10
Sage 1: Solve one equation for a variable:
S2_____
Sage 2: Substitute answer into the second equation and solve.
S1_____
Sage 1: Substitute answer and solve for the second variable.
S2_____
Sage 2: State the solution.
S1_____
5.
Equations: 2x + y = 3
3x + y = 0
Sage 1: Solve one equation for a variable:
S2_____
Sage 2: Substitute answer into the second equation and solve.
S1_____
Sage 1: Substitute answer and solve for the second variable.
S2_____
Sage 2: State the solution.
S1_____
3

4. 3.2 + 3.3 kids notes Substitution.notebook September 11, 2012
Section 3.2 p 135
# 11 ­ 16 all
discuss
Linear Combination Goal ­ eliminate one variable
Look for opposites.
6. 3x ­ 2y = 4
4x + 2y = 10
4

5. 3.2 + 3.3 kids notes Substitution.notebook September 11, 2012
7. 4x + 3y = 5
2x ­ 5y = ­17
4x + 3y = 5
2x ­ 5y = ­17
Steps:
1. Multiply
2. Add
2. Substitute
8. ­3x + 5y = ­6
6x ­ 10 y = 12
5

6. 3.2 + 3.3 kids notes Substitution.notebook September 11, 2012
9. 2x ­ 3y = 6
4x ­ 5y = 8
6