7.3.1 Products and Factors of Polynomials Products and Factors of Polynomials Objectives: Multiply and factor polynomials Use the Factor Theorem to solve problems

Real-World Application Objective: Multiply and factor polynomials

Real-World Application Objective: Multiply and factor polynomials

If I wanted to maximize the volume of this open-top box, what do you hypothesize I would need to do? In other words, what important information do I need to find? Collins Type 1 Objective: Multiply and factor polynomials

Example 1 Write the function f(x) = (x – 1)(x + 4)(x – 3) as a polynomial function in standard form. (x – 1)(x + 4)(x – 3) = (x – 1) = x(x 2 + x – 12) [(x + 4)(x – 3)] (x 2 + x – 12) – 1(x 2 + x – 12) = x 3 + x 2 – 12x– x 2 – x+ 12 = x 3 – 13x + 12 f(x) = x 3 – 13x + 12 Objective: Multiply and factor polynomials

Example 2 Factor each polynomial. a) x 3 – 16x xxxx = x(x 2 – 16x + 64) = x(x – 8)(x – 8) b) x 3 + 6x 2 – 5x - 30 = (x 3 + 6x 2 ) + (-5x – 30) = x 2 (x + 6) – 5(x + 6) = (x + 6)(x 2 – 5) (x + 6) Objective: Multiply and factor polynomials

Factoring the Sum and Difference of Two Cubes a 3 + b 3 = a 3 - b 3 = (a + b)(a 2 – ab + b 2 ) (a - b)(a 2 + ab + b 2 ) Objective: Multiply and factor polynomials

Example 3 Factor each polynomial. a) x b) x = x = (x + 5)(x 2 – 5x + 25) = x = (x - 3)(x 2 + 3x + 9) Objective: Multiply and factor polynomials

Factor Theorem x – r is a factor of the polynomial expression that defines the function P iff r is a solution of P(x) = 0, that is, iff P(r) = 0. Objective: Use the Factor Theorem to solve problems

Example 4 Use substitution to determine whether x – 1 is a factor of x 3 – x 2 – 5x – 3. Let x 3 – x 2 – 5x – 3 = 0 f(1) = (1) 3 – (1) 2 – 5(1) - 3 f(1) = 1 – 1 – f(1) = -8 Since f(1) does not equal zero, x – 1 is not a factor. Objective: Use the Factor Theorem to solve problems

Practice 1) Factor each polynomial. 2) Use substitution to determine whether x + 3 is a factor of x 3 – 3x 2 – 6x + 8. x x Objective: Use the Factor Theorem to solve problems

Collins Type 2 If p(-2) = 0, what does that tell you about the graph of p(x)? Objective: Use the Factor Theorem to solve problems

Homework Lesson 7.3 Exercises odd

7.3.2 Products and Factors of Polynomials Products and Factors of Polynomials Objectives: Divide one polynomial by another synthetic division Divide one polynomial by another using long division

Example 1 Use synthetic division to find the quotient: (6 – 3x 2 + x + x 3 ) ÷ (x – 3) Are the conditions for synthetic division met? Objective: Divide one polynomial by another using synthetic division Step 1: Write the opposite of the constant of the divisor on the shelf, and the coefficients of the dividend (in order) on the right.

Example 1 Use synthetic division to find the quotient: (x 3 – 3x 2 + x + 6) ÷ (x – 3) Step 2: Bring down the first coefficient under the line. Objective: Divide one polynomial by another using synthetic division

Example 1 Use synthetic division to find the quotient: (x 3 – 3x 2 + x + 6) ÷ (x – 3) Step 3: Multiply the number on the shelf, 3, by the number below the line and write the product below the next coefficient Objective: Divide one polynomial by another using synthetic division

Example 1 Use synthetic division to find the quotient: (x 3 – 3x 2 + x + 6) ÷ (x – 3) Step 4: Write the sum of -3 and 3 below the line Objective: Divide one polynomial by another using synthetic division

Example 1 Use synthetic division to find the quotient: (x 3 – 3x 2 + x + 6) ÷ (x – 3) Repeat steps 3 and Objective: Divide one polynomial by another using synthetic division

Example 1 Use synthetic division to find the quotient: (x 3 – 3x 2 + x + 6) ÷ (x – 3) Repeat steps 3 and Objective: Divide one polynomial by another using synthetic division

Example 1 (x 3 – 3x 2 + x + 6) ÷ (x – 3) The remainder is 9 and the resulting numbers are the coefficients of the quotient. x x – 3 9 Use synthetic division to find the quotient: Objective: Divide one polynomial by another using synthetic division Remainder Answer:

Practice Group 1 & 5: Divide: (x 3 + 3x 2 – 13x - 15) ÷ (x – 3) Objective: Divide one polynomial by another using synthetic division Group 2 & 6: Divide: (x 3 - 2x 2 – 22x + 40) ÷ (x – 4) Group 3 & 7: Divide: (x ) ÷ (x – 3) Group 4 & 8: Divide: (x 5 + 6x 3 - 5x 4 + 5x - 15) ÷ (x – 3)

Do you remember long division? Using long division: 745 ÷ Answer: Objective: Divide one polynomial by another using long division

(–14x + 56) x – 4x 3 – 2x 2 – 22x + 40 x2x2 (x 3 – 4x 2 ) 2x 2 + 2x (2x 2 – 8x) –14x – 14 – 16 x 2 + 2x – 14 – x – 4 16 Example 2 Using long division: (x 3 – 2x 2 – 22x + 40) ÷ (x – 4) x – Objective: Divide one polynomial by another using long division - - – – 22x + 40 Answer:

Example 3 Use long division to determine if x 2 + 3x + 2 is a factor of x 3 + 6x x + 6. x 2 + 3x + 2x 3 + 6x x + 6 (x 3 + 3x 2 + 2x ) 3x 2 + 9x x (3x 2 + 9x + 6) x 2 + 3x + 2 is a factor because the remainder is Objective: Divide one polynomial by another using long division - -

Practice Group 4 & 8: Divide: (x 3 + 3x 2 – 13x - 15) ÷ (x 2 – 2x – 3) Objective: Divide one polynomial by another using long division Group 3 & 7: Divide: (x 3 + 6x 2 – x - 30) ÷ (x 2 + 8x + 15) Group 2 & 6: Divide: (10x - 5x 2 + x ) ÷ (x 2 – x + 6) Group 1 & 5: Divide: (x 3 - 8) ÷ (x 2 – 2x + 4)

Collins Type 1 When dividing x x x + 45 by x + 5, would you use synthetic division or long division? Explain why. Objective: Divide one polynomial by another

Homework Lesson 7.3 Read Textbook Pages Exercises odd

Example 3 Given that 2 is a zero of P(x) = x 3 – 3x 2 + 4, use division to factor x 3 – 3x Since 2 is a zero, x = 2, so x – 2 = 0, which means x – 2 is a factor of x 3 – 3x (x 3 – 3x 2 + 4) ÷ (x – 2) Method 1 Method 2 - (–2x + 4) x – 2x 3 – 3x 2 + 0x + 4 x2x2 - (x 3 – 2x 2 ) -x 2 + 0x - x - (-x 2 + 2x) –2x + 4 – x 3 – 3x = (x – 2)(x 2 – x – 2) Objective: Divide one polynomial by another

Practice Given that -3 is a zero of P(x) = x 3 – 13x - 12, use division to factor x 3 – 13x – 12. Objective: Divide one polynomial by another Groups 1-4 use Method 1 (Long Division) Groups 5-8 use Method 2 (Synthetic Division)

Remainder Theorem If the polynomial expression that defines the function of P is divided by x – a, then the remainder is the number P(a). Objective: Use the Remainder Theorem to solve problems

Example 6 Given P(x) = 3x 3 – 4x 2 + 9x + 5 is divided by x – 6, find the remainder Method 1 Method 2 P(6) = 3(6) 3 – 4(6) 2 + 9(6) + 5 = 3(216) – 4(36) = 648 – = 563 Objective: Use the Remainder Theorem to solve problems

Practice Given P(x) = 3x 3 + 2x 2 + 3x + 1 is divided by x + 2, find the remainder. Objective: Use the Remainder Theorem to solve problems

A company manufactures cardboard boxes in the following way: they begin with 12"-by-18" pieces of cardboard, cut an x"-by-x" square from each of the four corners, then fold up the four flaps to make an open-top box. a.Sketch a picture or pictures of the manufacturing process described above. Label all segments in your diagram with their lengths (these will be formulas in terms of x). b.What are the length, width, and height of the box, in terms of x? c.Write a function V(x) expressing the volume of the box. d.Only some values of x would be meaningful in this problem. What is the interval of appropriate x-values? e.Using the interval you just named, make the graph V(x) on your calculator, then sketch it on paper. f.What value of x would produce a box with maximum volume? g.What are the dimensions and the volume for the box of maximum volume?