Multiplying Polynomials

Mastering the FOIL method and more

Introduction

  • Multiplying polynomials involves multiplying each term in one polynomial by each term in the other polynomial.
  • FOIL is a mnemonic device that helps us remember the order of multiplication: First, Outer, Inner, Last.
  • Like terms are terms with the same variables raised to the same power.

FOIL Method

  • To multiply a binomial by another binomial using the FOIL method:
  • - Multiply the First terms.
  • - Multiply the Outer terms.
  • - Multiply the Inner terms.
  • - Multiply the Last terms.
  • Combine like terms, if any.

Example 1: Multiplying Binomials

  • Multiply (x + 2) by (x + 5).
  • Using the FOIL method:
  • - First: x * x = x^2
  • - Outer: x * 5 = 5x
  • - Inner: 2 * x = 2x
  • - Last: 2 * 5 = 10
  • Combine like terms: 5x + 2x = 7x
  • Final result: x^2 + 7x + 10

Example 2: Squaring a Binomial

  • Square (x + 3).
  • Using the shortcut:
  • - Square the first term: x^2
  • - Double the product of the terms: 2(x * 3) = 6x
  • - Square the last term: 3^2 = 9
  • Final result: x^2 + 6x + 9

Example 3: Identical Brackets with Opposite Signs

  • Multiply (x - 5) by (x + 5).
  • Using the FOIL method:
  • - First: x * x = x^2
  • - Outer: x * 5 = 5x
  • - Inner: -5 * x = -5x
  • - Last: -5 * 5 = -25
  • Combine like terms: 5x + (-5x) = 0
  • Final result: x^2 - 25

Example 4: Squaring a Binomial with Opposite Signs

  • Square (2p - 3).
  • Using the shortcut:
  • - Square the first term: (2p)^2 = 4p^2
  • - Double the product of the terms: 2 * 2p * (-3) = -12p
  • - Square the last term: (-3)^2 = 9
  • Final result: 4p^2 - 12p + 9

Special Cases: Squaring a Binomial

  • When we square a binomial, we can use the FOIL method or the shortcut.
  • Shortcut: Square the first term, double the product of the terms, square the last term.
  • Shortcut example: (2x + 3)^2 = 4x^2 + 12x + 9
  • FOIL example: (2x + 3)(2x + 3) = 4x^2 + 6x + 6x + 9 = 4x^2 + 12x + 9

Conclusion

  • Multiplying polynomials requires careful multiplication of each term.
  • The FOIL method helps us keep track of the necessary multiplications and combining like terms.
  • Squaring a binomial can be done using a shortcut or the FOIL method, depending on our preference.
  • Understanding these techniques will help us simplify polynomial expressions and solve more complex equations.