Unit 6: Quadratic and Polynomial Functions

Topic 5

Adding, Subtracting, and Multiplying Polynomials

Polynomials are algebraic expressions made up of terms that include variables raised to whole-number powers. Examples: 3x2+5x23x^2 + 5x - 2, x34xx^3 - 4x, and 2x2+72x^2 + 7.
Operations on polynomials follow the same rules as arithmetic, except that we combine like terms—those with the same variable and exponent.
Like terms: 4x2 and 3x2(both have x2)\text{Like terms: } 4x^2 \text{ and } -3x^2 \quad \text{(both have } x^2\text{)}
Unlike terms: x2 and x3\text{Unlike terms: } x^2 \text{ and } x^3
1. Adding and Subtracting Polynomials To add or subtract, align like terms and combine their coefficients.
(3x2+2x+5)+(4x2x2)=7x2+x+3(3x^2 + 2x + 5) + (4x^2 - x - 2) = 7x^2 + x + 3
(5x32x2+x)(3x3+4x6)=2x32x23x+6(5x^3 - 2x^2 + x) - (3x^3 + 4x - 6) = 2x^3 - 2x^2 - 3x + 6
2. Multiplying Polynomials Use the Distributive Property or FOIL for binomials:
(a+b)(c+d)=ac+ad+bc+bd(a + b)(c + d) = ac + ad + bc + bd
(x+3)(x+5)=x2+8x+15(x + 3)(x + 5) = x^2 + 8x + 15
When multiplying larger polynomials, multiply each term in one by each term in the other and then combine like terms.
(x+2)(x2+3x+4)=x3+3x2+4x+2x2+6x+8=x3+5x2+10x+8(x + 2)(x^2 + 3x + 4) = x^3 + 3x^2 + 4x + 2x^2 + 6x + 8 = x^3 + 5x^2 + 10x + 8
3. Special Products to Remember
(a+b)2=a2+2ab+b2(a + b)^2 = a^2 + 2ab + b^2
(ab)2=a22ab+b2(a - b)^2 = a^2 - 2ab + b^2
(a+b)(ab)=a2b2(a + b)(a - b) = a^2 - b^2
Recognizing these patterns can save time on the SAT.

Core Skills

  • Identify and combine like terms correctly.
  • Apply distributive property to multiply expressions.
  • Recognize and expand special product patterns.
  • Simplify expressions by collecting terms and ordering by degree.
  • Apply these operations in context problems (area, expansion, algebraic structure).

Example 1: Adding Polynomials

Simplify:
(2x2+3x4)+(x25x+6)(2x^2 + 3x - 4) + (x^2 - 5x + 6)
Combine like terms:
(2x2+x2)+(3x5x)+(4+6)=3x22x+2.(2x^2 + x^2) + (3x - 5x) + (-4 + 6) = 3x^2 - 2x + 2.
Result: 3x22x+2\boxed{3x^2 - 2x + 2}

Example 2: Subtracting Polynomials

Simplify:
(4x32x+5)(x3+3x7)(4x^3 - 2x + 5) - (x^3 + 3x - 7)
Distribute the negative:
4x32x+5x33x+7=3x35x+12.4x^3 - 2x + 5 - x^3 - 3x + 7 = 3x^3 - 5x + 12.
Result: 3x35x+12\boxed{3x^3 - 5x + 12}

Example 3: Multiplying Binomials (FOIL)

Simplify:
(x+4)(x+6)(x + 4)(x + 6)
Use FOIL (First, Outer, Inner, Last):
x2+6x+4x+24=x2+10x+24.x^2 + 6x + 4x + 24 = x^2 + 10x + 24.
Result: x2+10x+24\boxed{x^2 + 10x + 24}

Example 4: Difference of Squares

Simplify:
(3x+5)(3x5)(3x + 5)(3x - 5)
=(3x)252=9x225.= (3x)^2 - 5^2 = 9x^2 - 25.
Result: 9x225\boxed{9x^2 - 25}

Example 5: Squaring a Binomial

Simplify:
(x+3)2=(x+3)(x+3)=x2+6x+9.(x + 3)^2 = (x + 3)(x + 3) = x^2 + 6x + 9.
Result: x2+6x+9\boxed{x^2 + 6x + 9}

Example 6: Area Application

The length of a rectangle is (x+4)(x + 4) and the width is (x+2)(x + 2). Find the area as a polynomial.
A=(x+4)(x+2)=x2+6x+8.A = (x + 4)(x + 2) = x^2 + 6x + 8.
Area: x2+6x+8\boxed{x^2 + 6x + 8}

Key Takeaways

  • Combine only like terms when adding or subtracting.
  • Apply distributive property for multiplication.
  • Recognize shortcuts for special products to save time.
  • Always simplify and arrange terms in descending powers.
  • These operations appear in both algebraic and geometric SAT contexts.