1. Section 2.4: Reasoning with Properties from Algebra

2. Algebraic Properties of Equality
Properties are used to explain why certain steps are being taken, such as in solving an algebra equation.
Let a, b, and c be real numbers.
Addition Property of Equality
If a = b, then a + c = b + c
Subtraction Property of Equality
If a = b, then a - c = b – c
Multiplication Property of Equality
If a = b, then ac = bc
Division Property of Equality
If a = b and c ≠ 0, then a ÷ c = b ÷ c
Reflexive Property of Equality
For any real number a, a = a
Symmetric Property of Equality
If a = b, then b = a
Transitive Property of Equality
If a = b and b = c, then a = c
Substitution Property of Equality
If a = b, then a can be substituted for b in any equation or expression
Distributive Property
For any real number, a(b + c) = ab + ac

3. More Properties of Equality Used in Geometry
We can also use the algebraic properties of equality in geometry.
PROPERTIES OF LENGTH AND MEASURE
Segment Length
Angle Measure
Reflexive
For any segment AB, AB = AB
For any angle A, m<A = m<A
Symmetric
If AB = CD, then CD = AB
If m<A = m<B, then m<B = m<A
Transitive
If AB = CD and CD = EF, then AB = EF
If m<A = m<B and m<B = m<C, then m<A = m<C