Basic Math

Equivalent expressions | Sixth Grade

Equivalent Expressions - Sixth Grade

Complete Notes & Formulas

1. What are Equivalent Expressions?

Definition

Equivalent expressions are expressions that

have the SAME VALUE for ALL values of the variable

They look different but mean the same thing!

Examples

2(x + 3) and 2x + 6 are equivalent

3x + 5x and 8x are equivalent

4 + x and x + 4 are equivalent

2. Properties of Addition

Commutative Property of Addition

Changing the ORDER doesn't change the sum

a + b = b + a

Example: 5 + 3 = 3 + 5

Associative Property of Addition

Changing the GROUPING doesn't change the sum

(a + b) + c = a + (b + c)

Example: (2 + 3) + 4 = 2 + (3 + 4)

Identity Property of Addition

Adding ZERO doesn't change the number

a + 0 = a

Example: 7 + 0 = 7

3. Properties of Multiplication

Commutative Property of Multiplication

Changing the ORDER doesn't change the product

a × b = b × a

Example: 4 × 5 = 5 × 4

Associative Property of Multiplication

Changing the GROUPING doesn't change the product

(a × b) × c = a × (b × c)

Example: (2 × 3) × 4 = 2 × (3 × 4)

Identity Property of Multiplication

Multiplying by ONE doesn't change the number

a × 1 = a

Example: 9 × 1 = 9

Zero Property of Multiplication

Multiplying by ZERO always equals zero

a × 0 = 0

Example: 100 × 0 = 0

4. Distributive Property

The Most Important Property!

Multiply the number OUTSIDE by EACH term inside

a(b + c) = ab + ac

a(b − c) = ab − ac

Example 1: Using Distributive Property

Simplify: 3(x + 5)

3(x + 5)

= 3 × x + 3 × 5

= 3x + 15

Answer: 3x + 15

Example 2: With Subtraction

Simplify: 4(2x − 3)

4(2x − 3)

= 4 × 2x − 4 × 3

= 8x − 12

Answer: 8x − 12

Visual: Area Model for Distributive Property

Example: 3(x + 4) using area model

3x 12 x 4 3 → 3x + 12

Area = 3(x + 4) = 3x + 12

5. Factoring Using Distributive Property

What is Factoring?

Factoring is REVERSE of distributing

Take OUT the common factor

ab + ac = a(b + c)

Steps to Factor

Step 1: Find the Greatest Common Factor (GCF)

Step 2: Divide each term by the GCF

Step 3: Write as: GCF(remaining terms)

Example 1: Factor 6x + 9

Step 1: GCF of 6 and 9 is 3

Step 2: 6x ÷ 3 = 2x, and 9 ÷ 3 = 3

Step 3: 3(2x + 3)

Answer: 3(2x + 3)

Example 2: Factor 4x + 8y

Step 1: GCF of 4x and 8y is 4

Step 2: 4x ÷ 4 = x, and 8y ÷ 4 = 2y

Step 3: 4(x + 2y)

Answer: 4(x + 2y)

6. Combining Like Terms

What are Like Terms?

Like terms have the SAME variable

with the SAME exponent

Only coefficients can be different

Like Terms vs Unlike Terms

Like Terms ✓Unlike Terms ✗
3x and 5x3x and 5y
7y and -2y7x and 7x²
4 and 9 (constants)4x and 9

How to Combine Like Terms

Add or subtract the COEFFICIENTS

Keep the VARIABLE the same

Example 1: Combine 4x + 7x

4x + 7x

= (4 + 7)x

= 11x

Answer: 11x

Example 2: Simplify 5x + 3 - 2x + 7

Step 1: Group like terms

(5x - 2x) + (3 + 7)

Step 2: Combine each group

3x + 10

Answer: 3x + 10

7. Writing Equivalent Expressions Using Properties

Methods to Create Equivalent Expressions

1. Use Distributive Property (expand)

2. Factor expressions (reverse distribute)

3. Combine like terms

4. Use commutative property (change order)

5. Use associative property (change grouping)

Example: Multiple Equivalent Forms

Original: 2(3x + 4)

Equivalent Form 1: 6x + 8 (using distributive)

Equivalent Form 2: 2(4 + 3x) (using commutative)

Equivalent Form 3: 2 × 3x + 2 × 4 (expanded)

All equal 6x + 8!

8. How to Identify Equivalent Expressions

Method 1: Simplify Both Expressions

Simplify each expression completely

If they simplify to the SAME form, they're equivalent

Example: Are 3(x + 2) and 3x + 6 equivalent?

Expression 1: 3(x + 2)

= 3x + 6

Expression 2: 3x + 6

= 3x + 6

Yes! They are equivalent ✓

Method 2: Substitute a Value

Test: Are 2x + 4 and 2(x + 2) equivalent?

Let x = 3

Expression 1: 2(3) + 4 = 10

Expression 2: 2(3 + 2) = 10

Both equal 10, so they're equivalent! ✓

9. Using Strip Models for Equivalent Expressions

What is a Strip Model?

A visual bar divided into sections

Each section represents a term

Helps see if expressions are equivalent

Visual Example: x + x + x = 3x

x + x + x = x x x 3x = 3x ✓ EQUIVALENT!

Both strips show the same total length

Quick Reference: Properties Summary

PropertyFormulaWhat It Does
Commutative (Addition)a + b = b + aChange order
Associative (Addition)(a + b) + c = a + (b + c)Change grouping
Distributivea(b + c) = ab + acMultiply each term
Identity (Addition)a + 0 = aAdd zero
Identity (Multiplication)a × 1 = aMultiply by one

💡 Important Tips to Remember

Distributive Property: Multiply OUTSIDE by EACH term inside

Factoring: Reverse of distributive (pull out GCF)

Like Terms: Must have same variable AND exponent

Combining: Add/subtract coefficients, keep variable

Commutative: Change order (works for + and ×)

Associative: Change grouping (works for + and ×)

Equivalent: Same value for all variable values

Check equivalence: Simplify both or substitute

Area models help visualize distributive property

Strip models help visualize equivalent expressions

🧠 Memory Tricks & Strategies

Distributive Property:

"Distribute means hand out - multiply outside with each inside, no doubt!"

Commutative:

"Commute means travel around - order can change, result stays sound!"

Associative:

"Associate means hang out together - parentheses move, still same forever!"

Like Terms:

"Same variable, same power - that's when you can combine in the hour!"

Factoring:

"Pull out what's common, that's the way - GCF comes first, terms inside stay!"

Master Equivalent Expressions! 🔢 ↔️ 🎯

Remember: Different looks, same value!

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