Welcome to class.

♥Please get your folders.

♥I need a couple of volunteers to hand out papers from the black tray.

♥We are going to go over your last quiz and grade homework before we take today’s quiz.

♥Eventually you will need a scissors and a glue stick

2.5 Reasoning in Algebra and Geometry

♥We accept postulates as true.

♥We also accept the properties of equality from algebra as true.

Other things we know are true

♥We know the distributive property is true:

♥And these properties of congruence:

Justifying Steps When Solving an Equation

What is the value of x?Justify each step.

1. <AOM and <MOC are supplementary

2. m<AOM + m<MOC = 180

3. (2x + 30) + x = 180

4. 3x +30 = 180

5. 3x = 150

6. X = 50

(2x + 30)◦ x◦A O C

M

1. Angles that form a linear pair are supplementary

2. Definition of supplementary <s

3. Substitution Property

4. Distributive Property

5. Subtraction Property of Equality

6. Division Property of Equality

PROOFThis will be your new best friend. Spend a lot of time with it ♥

♥A proof is a convincing argument that uses deductive reasoning.

♥A proof logically shows why a conjecture is true.♥A two-column proof lists each statement on the left and the justification, or reason, on the right.♥Each statement must follow logically from the steps before it.

Two-Column Proof

Your assignment

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