Learn on PengiAoPS: Introduction to Algebra (AMC 8 & 10)Chapter 4: More Variables

Lesson 3: Distribution and Factoring

In this Grade 4 lesson from AoPS: Introduction to Algebra, students learn how to apply the distributive property and factoring with multiple variables, extending the same techniques used with single variables and constants. Through real-world problems involving baseball and football team rosters, students practice expanding expressions like 7(2x + 4y) = 14x + 28y and simplifying multi-variable expressions by distributing subtraction across parentheses. This lesson builds fluency with core algebraic manipulation skills essential for AMC 8 and AMC 10 competition math.

Section 1

Multiplying by a monomial

Property

To multiply a polynomial by a monomial, we use the distributive law. This means we multiply each term of the polynomial by the monomial.

a(b+c)=ab+aca(b + c) = ab + ac

Examples

  • To multiply 4x(2x25x+3)4x(2x^2 - 5x + 3), distribute 4x4x to each term: 4x(2x2)+4x(5x)+4x(3)=8x320x2+12x4x(2x^2) + 4x(-5x) + 4x(3) = 8x^3 - 20x^2 + 12x.

Section 2

Factor out the GCF

Property

We use the Distributive Property in reverse to factor a polynomial. Find the GCF of all the terms and write the polynomial as a product.

Distributive Property:
If aa, bb, and cc are real numbers, then a(b+c)=ab+aca(b + c) = ab + ac and ab+ac=a(b+c)ab + ac = a(b + c). The form on the right is used to factor.

To factor the GCF from a polynomial:
Step 1. Find the GCF of all terms.
Step 2. Rewrite each term as a product using the GCF.
Step 3. Use the “reverse” Distributive Property to factor the expression.
Step 4. Check by multiplying the factors.

Book overview

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Chapter 4: More Variables

  1. Lesson 1

    Lesson 1: Evaluating Multi-Variable Expressions

  2. Lesson 2

    Lesson 2: Still More Arithmetic

  3. Lesson 3Current

    Lesson 3: Distribution and Factoring

  4. Lesson 4

    Lesson 4: Fractions

  5. Lesson 5

    Lesson 5: Equations

Lesson overview

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Section 1

Multiplying by a monomial

Property

To multiply a polynomial by a monomial, we use the distributive law. This means we multiply each term of the polynomial by the monomial.

a(b+c)=ab+aca(b + c) = ab + ac

Examples

  • To multiply 4x(2x25x+3)4x(2x^2 - 5x + 3), distribute 4x4x to each term: 4x(2x2)+4x(5x)+4x(3)=8x320x2+12x4x(2x^2) + 4x(-5x) + 4x(3) = 8x^3 - 20x^2 + 12x.

Section 2

Factor out the GCF

Property

We use the Distributive Property in reverse to factor a polynomial. Find the GCF of all the terms and write the polynomial as a product.

Distributive Property:
If aa, bb, and cc are real numbers, then a(b+c)=ab+aca(b + c) = ab + ac and ab+ac=a(b+c)ab + ac = a(b + c). The form on the right is used to factor.

To factor the GCF from a polynomial:
Step 1. Find the GCF of all terms.
Step 2. Rewrite each term as a product using the GCF.
Step 3. Use the “reverse” Distributive Property to factor the expression.
Step 4. Check by multiplying the factors.

Book overview

Jump across lessons in the current chapter without opening the full course modal.

Continue this chapter

Chapter 4: More Variables

  1. Lesson 1

    Lesson 1: Evaluating Multi-Variable Expressions

  2. Lesson 2

    Lesson 2: Still More Arithmetic

  3. Lesson 3Current

    Lesson 3: Distribution and Factoring

  4. Lesson 4

    Lesson 4: Fractions

  5. Lesson 5

    Lesson 5: Equations