Algebra 1

Lesson 2.8

Algebraic Proof

What do you know about Algebraic Proof?

Think-Pair-Share

Prove it!

ConceptWhy are we able to...-frying pan

-heat

-muscles

- law of gravity

- soap & water- washing machine-dryer

Prove that your BF is cheating on you...

(

(some proof) (more proof)

JB is cheating on Ms. Vallejo!

Prove: 9=5+4

Prove...

Statement Reason(What you did) (What allowed you to do that?)

1. 9=5+4 1. Given2. 9=9 2. Addition

Prove: -5 = 3x+1

Prove...

Statement Reason(What you did) (What allowed you to do that)

1. -5 = 3x + 1 1. Given

2. 6 = 3x 2. subtraction Prop of equality

-1 -1

/3 /3

3. 2=x 3. division Prop of equality

Given: 5x - 4 = 6 Prove: x=3

Prove...

Statement Reason(What you did) (What allowed you to do that?)

1. 5x - 4 = 6+4 +4

2. 5x = 10/5 /5

3. x= 2

1. Given

2. Addition prop of equality

3. division Prop of Equality

Given: 2x - 30 = -4x + 6

Prove...

Statement Reason(What you did) (What allowed you to do that?)

1. 2x - 30 = -4x + 6+ 4x +4x

2. 6x - 30 = 6+30 +30

3. 6x = 36/6 /6

4. x = 6

1. Given

2. Addition prop of Eq.

3. Addition prop of Eq

4. Division prop of Eq

10

10

1. Given2. Distributive Prop.

3. Assoc. Prop of Add.4. Addition

1. Given2. Commu. Prop of Mult.

3. Addition4. Commu. Prop of Add.

1. Given2. Comm. Prop of Mult. 3. Assoc Prop of Mult.

4. Multiplication5. Addition

1. Comm.P of Mult2. Mult.

3. Addition

Commutative Property

of Addition

A B = C

B A C