1. Obj: To use properties of equality in algebraic and geometric proofs
2.4 Using Proof in Algebra
Obj: To use properties of equality in algebraic and geometric proofs

2. Types of Proofs 2-column Paragraph (AKA informal proof)
Flow proof (looks like a flow chart)

3. Example: Prove it! If 3x + 6 = 12, then x = 2 Solve 3x + 6 = 12 3x = 6
Statement
Justification
2- column proof
1.) 3x + 6 = 12
1.) Given
2.) 3x = 6
2.) Subtraction prop.
3.) x = 2
3.) division prop.
Hypothesis: AKA Given
Conclusion: Final statement

4. Your Turn: Prove if then x = 2/3 1.) 3x + 8 5 = 2 1.) Given
Statement Justification
1.) 3x + 8 5 = 2
1.) Given
2.) 3x + 8 = 10
2.) Mult. prop
3.) 3x = 2
3.) subtract prop.
4.) x = 2/3
4.) division prop

5. Prove:
If 3(x - 4) + 2(x + 6) = 10 then x = 2
Statement Justification

6. Properties: Check the properties on page 107.
Are there any questions or explanations needed?

7. Homework:
Put this in your agenda:
Pg – 25 odd, 26,

8. Example: If
&
are complementary then
is a right angle.

9. Answer to example: 1.) are complementary 1.) Given
Statement
Justification
1.)
are complementary
1.)
Given
2.) Def of comp. angles
3.) angle + post
4.) Substitution
is a rt. angle
5.) Def. of rt. angle