1. Section 2.4 Algebraic Reasoning
Student Learning Goal: Students will justify steps for solving equations using Algebraic Properties of Equality and then apply those properties to segment lengths and angle measurements
Homework: Worksheet

2. Solving an equation, you used properties of real numbers
Examples:
1) x + 5 = 21
2) ( 2x +5) = 21
Segment lengths and angle measurements are real numbers, so you can use these properties to write logical arguments about geometric figures.

4. Example 1: State the property that justifies each statement.
If m ∠A = m∠B and m∠B = m∠C, then m∠A =m∠C
If m ∠1 + m∠2 = 90 and m∠2 = m∠3, then m∠1 + m∠3 = 90
∠A = ∠A
If JK ≅ LM, then LM ≅ JK
If HJ + 5 = 20 , then HJ = 15
If AB = 14 and CD = 1, then AB = CD

5. Example 2: Solve 3x + 2 = 23-4x Justify each step.
Equation
Reason
3x + 2 = x
Given
3x = x
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3x = x
Substitution/Simplify
3x + 4x = x + 4x
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7x = 21
Division Property
x = 3

6. Example 3: Solve : 5(7x - 8) = 30 Justify each step
Example 3: Solve : 5(7x - 8) = 30 Justify each step. Show 2 different ways. 1st way: 2nd way:
Equation
Reason
5( 7x - 8) =30
Given
35x -40 = 30
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35x =
35x = 70
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x = 2