# 6.2 Substitution

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```					       6.2 Substitution

Objective:
A) Solve systems of equations by using
substitution
B) Solve real world problems involving
systems of equations by using
substitution
Substitution

A method of finding an
exact solution of a
system of equations
Steps for solving a system of
equations by Substitution
Step 1: When necessary,
solve at least one
equation for one variable
Step 2: Substitute the
resulting expression from
Step 1 into the other
equation to replace the
variable. Then solve the
equation.
Step 3: Substitute the
value from Step 2 into
either equation, and solve
for the other variable.
Write the solution as an
ordered pair.
Example 1- Solve the System of
Equations
y = 2x + 1
3x + y = -9
Example 2- Solve the System of
Equations
y = 4x –6
5x +3y = -1
You Try
Page 345 #1 and 2
Solve and then Substitute
Example 1

x + 2y = 6
3x – 4y = 28
Example 2- Solve and Then
Substitute
4x + 5y = 11
y – 3x = -13
You Try

Page 345 # 3
No Solution or Infinitely Many
Solutions
Example 1
y = 2x –4
-6x + 3y = - 12
Example 2- Solve the System of
Equations
2x – y =8
y = 2x - 3
You Try
Page 345 #4 and 5
Write and Solve a System of
Equations
Page 344
A store sold a total of 125 car stereo systems
and speakers in one week. The stereo
systems sold for \$104.95, and the speakers
sold for \$18.95. The sales from these two
items totaled \$6926.75. How many of
each item were sold?
Homework

Page 345 # 9 to 22 odd,
Skip 15

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