Learn on PengiSaxon Algebra 2Chapter 2: Lessons 11-20, Investigation 2

Lesson 19: Multiplying Polynomials

In this Grade 10 Saxon Algebra 2 lesson, students learn how to multiply polynomials using the FOIL method for binomials, the distributive property for larger expressions, and special product patterns including the sum and difference, square of a sum, and square of a difference. The lesson also covers multiplying three or more polynomials using the Associative Property of Multiplication. Students apply these skills to real-world problems, such as writing a polynomial expression to represent the area of a geometric figure.

Section 1

πŸ“˜ Multiplying Polynomials

New Concept

To multiply two polynomials, each term of the first polynomial is multiplied by each term of the other polynomial.

What’s next

Next, you’ll learn the FOIL method for multiplying binomials and memorize special product patterns to increase your speed and accuracy.

Section 2

The FOIL Method

To multiply two binomials, multiply the First terms, Outside terms, Inside terms, and Last terms. After finding these four products, combine the like terms to get the final answer.

Example 1: To solve (x+6)(xβˆ’3)(x + 6)(x - 3), we follow FOIL. F: xβ‹…x=x2x \cdot x = x^2. O: xβ‹…(βˆ’3)=βˆ’3xx \cdot (-3) = -3x. I: 6β‹…x=6x6 \cdot x = 6x. L: 6β‹…(βˆ’3)=βˆ’186 \cdot (-3) = -18. Combine them: x2βˆ’3x+6xβˆ’18=x2+3xβˆ’18x^2 - 3x + 6x - 18 = x^2 + 3x - 18.
Example 2: To solve (2yβˆ’4)(3y+5)(2y - 4)(3y + 5), we follow FOIL. F: 2yβ‹…3y=6y22y \cdot 3y = 6y^2. O: 2yβ‹…5=10y2y \cdot 5 = 10y. I: βˆ’4β‹…3y=βˆ’12y-4 \cdot 3y = -12y. L: βˆ’4β‹…5=βˆ’20-4 \cdot 5 = -20. Combine them: 6y2+10yβˆ’12yβˆ’20=6y2βˆ’2yβˆ’206y^2 + 10y - 12y - 20 = 6y^2 - 2y - 20.

Think of FOIL as a four-step dance for binomials! It's a super handy acronym that guarantees you multiply every term from the first parenthesis with every term from the second. By following the First, Outside, Inside, and Last steps, you ensure no combination is missed, making complex multiplications simple and organized. It's your foolproof map to the correct answer.

Section 3

Sum and difference

The product of the sum and difference of the same two terms follows the pattern: (a+b)(aβˆ’b)=a2βˆ’b2(a + b)(a - b) = a^2 - b^2.

Example 1: (3x+4y)(3xβˆ’4y)=(3x)2βˆ’(4y)2=9x2βˆ’16y2(3x + 4y)(3x - 4y) = (3x)^2 - (4y)^2 = 9x^2 - 16y^2.
Example 2: (z+8)(zβˆ’8)=z2βˆ’82=z2βˆ’64(z + 8)(z - 8) = z^2 - 8^2 = z^2 - 64.

This is the ultimate shortcut for multiplying conjugate pairs! When you see two binomials with the exact same terms but opposite signs, the 'Outside' and 'Inside' products magically cancel each other out. This pattern lets you jump straight to the answer: just square the first term, square the second term, and put a minus sign between them!

Section 4

Square of a sum

The square of a binomial sum follows the pattern: (a+b)2=(a+b)(a+b)=a2+2ab+b2(a + b)^2 = (a + b)(a + b) = a^2 + 2ab + b^2.

Example 1: (4p+3q)2=(4p)2+2(4p)(3q)+(3q)2=16p2+24pq+9q2(4p + 3q)^2 = (4p)^2 + 2(4p)(3q) + (3q)^2 = 16p^2 + 24pq + 9q^2.
Example 2: (x+5)2=x2+2(x)(5)+52=x2+10x+25(x + 5)^2 = x^2 + 2(x)(5) + 5^2 = x^2 + 10x + 25.

Squaring a binomial isn't just squaring each piece inside! You're multiplying the binomial by itself, which requires the FOIL method. This pattern, a2+2ab+b2a^2 + 2ab + b^2, is a fantastic time-saver. It reminds you to always include the product of the 'Outside' and 'Inside' terms, which are always identical. This middle term is the secret ingredient!

Book overview

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Chapter 2: Lessons 11-20, Investigation 2

  1. Lesson 1

    Lesson 11: Understanding Polynomials

  2. Lesson 2

    Lesson 12: Solving Inverse Variation Problems

  3. Lesson 3

    Lab 3: Graphing Calculator: Calculating Points on a Graph

  4. Lesson 4

    Lesson 13: Graphing Linear Equations I

  5. Lesson 5

    Lesson 14: Finding Determinants

  6. Lesson 6

    Lesson 15: Solving Systems of Equations by Graphing

  7. Lesson 7

    Lesson 16: Using Cramer's Rule

  8. Lesson 8

    LAB 4: Graphing Calculator: Changing the Line and Window of a Graph

  9. Lesson 9

    Lesson 17: Solving Equations and Inequalities with Absolute Value (Exploration: Transforming f(x) = |x|)

  10. Lesson 10

    Lesson 18: Calculating with Units of Measure

  11. Lesson 11Current

    Lesson 19: Multiplying Polynomials

  12. Lesson 12

    Lesson 20: Performing Operations with Functions

  13. Lesson 13

    Investigation 2: Solving Parametric Equations

Lesson overview

Expand to review the lesson summary and core properties.

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Section 1

πŸ“˜ Multiplying Polynomials

New Concept

To multiply two polynomials, each term of the first polynomial is multiplied by each term of the other polynomial.

What’s next

Next, you’ll learn the FOIL method for multiplying binomials and memorize special product patterns to increase your speed and accuracy.

Section 2

The FOIL Method

To multiply two binomials, multiply the First terms, Outside terms, Inside terms, and Last terms. After finding these four products, combine the like terms to get the final answer.

Example 1: To solve (x+6)(xβˆ’3)(x + 6)(x - 3), we follow FOIL. F: xβ‹…x=x2x \cdot x = x^2. O: xβ‹…(βˆ’3)=βˆ’3xx \cdot (-3) = -3x. I: 6β‹…x=6x6 \cdot x = 6x. L: 6β‹…(βˆ’3)=βˆ’186 \cdot (-3) = -18. Combine them: x2βˆ’3x+6xβˆ’18=x2+3xβˆ’18x^2 - 3x + 6x - 18 = x^2 + 3x - 18.
Example 2: To solve (2yβˆ’4)(3y+5)(2y - 4)(3y + 5), we follow FOIL. F: 2yβ‹…3y=6y22y \cdot 3y = 6y^2. O: 2yβ‹…5=10y2y \cdot 5 = 10y. I: βˆ’4β‹…3y=βˆ’12y-4 \cdot 3y = -12y. L: βˆ’4β‹…5=βˆ’20-4 \cdot 5 = -20. Combine them: 6y2+10yβˆ’12yβˆ’20=6y2βˆ’2yβˆ’206y^2 + 10y - 12y - 20 = 6y^2 - 2y - 20.

Think of FOIL as a four-step dance for binomials! It's a super handy acronym that guarantees you multiply every term from the first parenthesis with every term from the second. By following the First, Outside, Inside, and Last steps, you ensure no combination is missed, making complex multiplications simple and organized. It's your foolproof map to the correct answer.

Section 3

Sum and difference

The product of the sum and difference of the same two terms follows the pattern: (a+b)(aβˆ’b)=a2βˆ’b2(a + b)(a - b) = a^2 - b^2.

Example 1: (3x+4y)(3xβˆ’4y)=(3x)2βˆ’(4y)2=9x2βˆ’16y2(3x + 4y)(3x - 4y) = (3x)^2 - (4y)^2 = 9x^2 - 16y^2.
Example 2: (z+8)(zβˆ’8)=z2βˆ’82=z2βˆ’64(z + 8)(z - 8) = z^2 - 8^2 = z^2 - 64.

This is the ultimate shortcut for multiplying conjugate pairs! When you see two binomials with the exact same terms but opposite signs, the 'Outside' and 'Inside' products magically cancel each other out. This pattern lets you jump straight to the answer: just square the first term, square the second term, and put a minus sign between them!

Section 4

Square of a sum

The square of a binomial sum follows the pattern: (a+b)2=(a+b)(a+b)=a2+2ab+b2(a + b)^2 = (a + b)(a + b) = a^2 + 2ab + b^2.

Example 1: (4p+3q)2=(4p)2+2(4p)(3q)+(3q)2=16p2+24pq+9q2(4p + 3q)^2 = (4p)^2 + 2(4p)(3q) + (3q)^2 = 16p^2 + 24pq + 9q^2.
Example 2: (x+5)2=x2+2(x)(5)+52=x2+10x+25(x + 5)^2 = x^2 + 2(x)(5) + 5^2 = x^2 + 10x + 25.

Squaring a binomial isn't just squaring each piece inside! You're multiplying the binomial by itself, which requires the FOIL method. This pattern, a2+2ab+b2a^2 + 2ab + b^2, is a fantastic time-saver. It reminds you to always include the product of the 'Outside' and 'Inside' terms, which are always identical. This middle term is the secret ingredient!

Book overview

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

Continue this chapter

Chapter 2: Lessons 11-20, Investigation 2

  1. Lesson 1

    Lesson 11: Understanding Polynomials

  2. Lesson 2

    Lesson 12: Solving Inverse Variation Problems

  3. Lesson 3

    Lab 3: Graphing Calculator: Calculating Points on a Graph

  4. Lesson 4

    Lesson 13: Graphing Linear Equations I

  5. Lesson 5

    Lesson 14: Finding Determinants

  6. Lesson 6

    Lesson 15: Solving Systems of Equations by Graphing

  7. Lesson 7

    Lesson 16: Using Cramer's Rule

  8. Lesson 8

    LAB 4: Graphing Calculator: Changing the Line and Window of a Graph

  9. Lesson 9

    Lesson 17: Solving Equations and Inequalities with Absolute Value (Exploration: Transforming f(x) = |x|)

  10. Lesson 10

    Lesson 18: Calculating with Units of Measure

  11. Lesson 11Current

    Lesson 19: Multiplying Polynomials

  12. Lesson 12

    Lesson 20: Performing Operations with Functions

  13. Lesson 13

    Investigation 2: Solving Parametric Equations