5-Minute Check 1

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5-Minute Check 1
BellRinger
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CCSS
Content Standards Preparation for G.CO.9 Prove
theorems about lines and angles. Mathematical
Practices 3 Construct viable arguments and
critique the reasoning of others.
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Then/Now
You used postulates about points, lines, and
planes to write paragraph proofs.

• Use algebra to write two-column proofs.

• Use properties of equality to write geometric
  proofs.

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Concept
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Example 1
Justify Each Step When Solving an Equation
Solve 2(5 3a) 4(a 7) 92.
Algebraic Steps Properties 2(5 3a) 4(a
7) 92 Original equation 10 6a 4a
28 92 Distributive Property 18
10a 92 Substitution Property 18 10a 18
92 18 Addition Property
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Example 1
Justify Each Step When Solving an Equation
10a 110 Substitution Property
Division Property
a 11 Substitution Property
Answer a 11
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Example 1
Solve 3(a 3) 5(3 a) 50.
A. a 12 B. a 37 C. a 7 D. a 7
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Example 2
Write an Algebraic Proof
Begin by stating what is given and what you are
to prove.
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Example 2
Write an Algebraic Proof
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Example 2
Which of the following statements would complete
the proof of this conjecture?
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Example 2
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Example 2
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• Groupwork P139 1-5
• Homework Worksheet 2-6

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Example 3
Write a Geometric Proof
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Example 3
Write a Geometric Proof
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Example 3
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Example 3
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Example 3
A. Reflexive Property of Equality B. Symmetric
Property of Equality C. Transitive Property of
Equality D. Substitution Property of Equality
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End of the Lesson