REASONING IN ALGEBRA PROPERTIES OF EQUALITY AND CONGRUENCE

Reflexive Property

The number equal to itself is called reflexive property in algebra.

Equality

AB = AB

m∠A = m∠A

Congruence

AB ≅ AB

∠A ≅ ∠A

Symmetric Property

Equality

If AB = CD, then CD = AB.

If m∠A = m∠B, then m∠B = m∠A.

Congruence

If AB ≅ CD, then CD ≅ AB.

If ∠A ≅ ∠B, then ∠B ≅ ∠A.

Transitive Property

Equality

If AB = CD and CD = EF, then AB = EF.

If m∠A = m∠B and m∠B = m∠C, then m∠A = m∠C.

Congruence

If AB ≅ CD and CD ≅ EF, then AB ≅ EF.

If ∠A ≅ ∠B and ∠B ≅ ∠C, then  ∠A ≅ ∠C.

PROPERTIES OF EQUALITY

Addition Property

Adding the same number to each side of an equation produces an equivalent equation.

Example

x - 3 = 7

x - 3 + 3 = 7 + 3

Subtraction Property

Subtracting the same number from each side of an equation produces an equivalent equation.

Example

y + 5 = 11

y + 5 - 5 = 11 - 5

Multiplication Property

Multiplying each side of an equation by the same nonzero number produces an equivalent equation.

Example

14z=614z4=64

Problem 1 :

Write the letter of each property next to its definition. The letters a, b, and c represent real numbers.

1. If a = b, then b = a

2. If a = b, then ac = bc

3. AB ≅ AB 

4. a = a

5. If a = b, then a + c = b + c

6. a(b + c) = ab + ac

7. If a = b and b = c, then a = c

8. If ∠P ≅ ∠Q, then ∠Q ≅ ∠P

9. If ∠A ≅ ∠B, and ∠B ≅ ∠C, then ∠A ≅ ∠C

10. If a = b and c ≠ 0, then a/c = b/c

11. If a = b, then b can be substituted for a in any expression

12. If a = b, then a - c = b - c

A. Addition Property of Equality

B. Subtraction Property of Equality

C. Multiplication Property of Equality

D. Division Property of Equality

E. Reflexive Property of Equality

F. Symmetric Property of Equality

G. Transitive Property of Equality

H. Substitution Property of Equality

I. Distributive Property

J. Reflexive Property of congruence

K. Symmetric Property of Congruence

L. Transitive Property of Congruence

Solution:

1. If a = b, then b = a. This is symmetric Property of Equality

2. If a = b, then ac = bc. This is Multiplication Property of Equality

3. AB ≅ AB. This is Reflexive Property of Congruence

4. a = a. This is Reflexive Property of Equality

5. If a = b, then a + c = b + c. This is Addition Property of Equality

6. a(b + c) = ab + ac. This is Distributive Property

7. If a = b and b = c, then a = c. This is Transitive Property of Equality

8. If ∠P ≅ ∠Q, then ∠Q ≅ ∠P. This is Symmetric Property of Congruence

9. If ∠A ≅ ∠B, and ∠B ≅ ∠C, then ∠A ≅ ∠C. This is Transitive Property of Congruence

10. If a = b and c ≠ 0, then a/c = b/c. This is Division Property of Equality

11. If a = b, then b can be substituted for a in any expression. This is Substitution Property of Equality

12. If a = b, then a - c = b - c. This is Subtraction Property of Equality

1. If a = b, then b = a

2. If a = b, then ac = bc

3. AB ≅ AB 

4. a = a

5. If a = b, then a + c = b + c

6. a(b + c) = ab + ac

7. If a = b and b = c, then a = c

8. If ∠P ≅ ∠Q, then ∠Q ≅ ∠P

9. If ∠A ≅ ∠B, and ∠B ≅ ∠C, then ∠A ≅ ∠C

10. If a = b and c ≠ 0, then a/c = b/c

11. If a = b, then b can be substituted for a in any expression

12. If a = b, then a - c = b - c

F. Symmetric Property of Equality

C. Multiplication Property of Equality

J. Reflexive Property of congruence

E. Reflexive Property of Equality

A. Addition Property of Equality

I. Distributive Property

G. Transitive Property of Equality

K. Symmetric Property of Congruence

L. Transitive Property of Congruence

D. Division Property of Equality

H. Substitution Property of Equality

B. Subtraction Property of Equality

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