Solving Two-Step Equations

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LESSON 3-4 Warm Up
Lesson 3-4 Warm Up
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LESSON 3-4 Warm Up
Lesson 3-4 Warm Up
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Solving Two-Step Equations (3-4)

• What is a two-step equation?
• How can you use a model to show how to solve a
  two-step equation?

• Two-Step Equation an equation that involves
  undoing two operations
• In the following model, represents -1,
  represents 1, and represents a variable, like x.
  This means that equals 0 (in other
  words, they cancel each other out), since 1 1
  0.

1
1
1
1
x
1
-1
x
x
cancel out (zero pair)
-x
1
1
1
1
1
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Solving Two-Step Equations (3-4)

• To solve equations, use the addition,
  subtraction, multiplication, and division
  properties of equality which say that the
  equation stays equal, or balanced, if you add,
  subtract, multiply, or divide both sides by the
  same number. Simply use the properties of
  equality repeatedly to get the variable alone on
  one side of the equation with a coefficient of 1
  (Examples 1x, 1t, 1c)

• How do you solve equations involving more than
  one step.

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Solving Two-Step Equations
LESSON 3-4
Additional Examples
Solve y 7 12.
y 7 12 Subtraction
Property of Equality - 7 - 7
y 19 Simplify.
(1)(y) (1)(19) Multiplication
Property of Equality
y 19 Simplify.
Check y 7 12
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Solving Two-Step Equations
LESSON 3-4
Additional Examples
Solve 2.25 8.5.
10
4
0
0
1
5 1
1
1
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Solving Two-Step Equations
LESSON 3-4
Additional Examples
The Science Club sells birdfeeders for 8
each. The club spends 32 in building materials.
The clubs profit is 128. How many birdfeeders
did the club sell?
0
1
1
1
The club sold 20 birdfeeders.
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Solving Two-Step Equations
LESSON 3-4
Additional Examples
y3
Solve 13 5.
0
1
31
24 y Simplify.
1
1
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Solving Two-Step Equations
LESSON 3-4
Additional Examples
You order iris bulbs from a catalog. Iris bulbs
cost 0.90 each. The shipping charge is 2.50. If
you have 18.50 to spend, how many iris bulbs can
you order?
0.90b 2.50 18.50
0.90b 2.50 18.50 Subtract 2.50 from each
side. 2.50 2.50
0.90b 16.00 Simplify.
0
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Solving Two-Step Equations
LESSON 3-4
Additional Examples
(continued)
1
1
You can order 17 bulbs.
Check  Is the solution reasonable? You can only
order whole iris bulbs. Since 18 bulbs would cost
18 0.90 16.20 plus 2.50 for shipping, which
is more than 18.50, you can only order 17 bulbs.
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Solving Two-Step Equations
LESSON 3-4
Lesson Quiz
Solve each equation. 1. 6a 12 30 2.
21 24 3. 4c 40 28 4. 15 22
b 5
3
15
d 7
17
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