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2.3 Add, Subtract, & Multiply Polynomials

2.3 Add, Subtract, & Multiply Polynomials. p. 104 What are the two ways that you can add, subtract or multiply polynomials? Name three special product patterns. To add or subtract, add or subtract the coefficients of like terms! Vertical format :. Add 3x 3 +2x 2 -x-7 and x 3 -10x 2 +8.

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2.3 Add, Subtract, & Multiply Polynomials

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  1. 2.3 Add, Subtract, & Multiply Polynomials p. 104 What are the two ways that you can add, subtract or multiply polynomials? Name three special product patterns.

  2. To add or subtract, add or subtract the coefficients of like terms!Vertical format : • Add 3x3+2x2-x-7 and x3-10x2+8. • 3x3 + 2x2 – x – 7 + x3 – 10x2 + 8 Line up like terms • 4x3 – 8x2 – x + 1

  3. Horizontal format: Combine like terms • (8x3 – 3x2 – 2x + 9) – (2x3 + 6x2 – x + 1)= • (8x3 – 2x3)+(-3x2 – 6x2)+(-2x + x) + (9 – 1)= • 6x3 + -9x2 + -x + 8 = • 6x3 – 9x2 – x + 8

  4. 8x3 – x2 – 5x + 1 8x3 – x2 – 5x + 1 – (3x3 + 2x2–x + 7) + – 3x3– 2x2 + x – 7 5x3 – 3x2 – 4x – 6 Subtract polynomials vertically a. Subtract 3x3 + 2x2 – x + 7 from 8x3 – x2 – 5x + 1 in a vertical format. SOLUTION a. Align like terms, then add the opposite of the subtracted polynomial.

  5. Subtract polynomials horizontally b. Subtract 5z2 – z + 3 from 4z2 + 9z – 12 in a horizontal format. Write the opposite of the subtracted polynomial, then add like terms. (4z2 + 9z – 12) – (5z2–z + 3) = 4z2 + 9z – 12 – 5z2 + z – 3 = 4z2 – 5z2 + 9z + z – 12 – 3 = – z2 + 10z – 15

  6. Examples: Adding & Subtracting • (9x3 – 2x + 1) + (5x2 + 12x -4) = • 9x3 + 5x2 – 2x + 12x + 1 – 4 = • 9x3 + 5x2 + 10x – 3 • (2x2 + 3x) – (3x2 + x – 4)= • 2x2 + 3x – 3x2 – x + 4 = • 2x2 - 3x2 + 3x – x + 4 = • -x2 + 2x + 4

  7. Multiplying Polynomials: Vertically • (-x2 + 2x + 4)(x – 3)= • -x2 + 2x + 4 × x – 3 3x2 – 6x – 12 -x3 + 2x2 + 4x -x3 + 5x2 – 2x – 12

  8. Multiplying Polynomials : Horizontally • (x – 3)(3x2 – 2x – 4)= • (x – 3)(3x2) • + (x – 3)(-2x) • + (x – 3)(-4) = • (3x3 – 9x2) + (-2x2 + 6x) + (-4x + 12) = • 3x3 – 9x2 – 2x2 + 6x – 4x +12 = • 3x3 – 11x2 + 2x + 12

  9. Multiplying 3 Binomials : • (x – 1)(x + 4)(x + 3) = • FOIL the first two: • (x2 – x +4x – 4)(x + 3) = • (x2 + 3x – 4)(x + 3) = • Then multiply the trinomial by the binomial • (x2 + 3x – 4)(x) + (x2 + 3x – 4)(3) = • (x3 + 3x2 – 4x) + (3x2 + 9x – 12) = • x3 + 6x2 + 5x - 12

  10. Some binomial products appear so much we need to recognize the patterns! • Sum & Difference (S&D): • (a + b)(a – b) = a2 – b2 • Example: (x + 3)(x – 3) = x2 – 9 • Square of Binomial: • (a + b)2 = a2 + 2ab + b2 • (a - b)2 = a2 – 2ab + b2

  11. Last Pattern • Cube of a Binomial • (a + b)3 = a3 + 3a2b + 3ab2 + b3 • (a – b)3 = a3 - 3a2b + 3ab2 – b3

  12. Example: (a + b)3 = a3 + 3a2b + 3ab2 + b3 • (x + 5)3 = • a=? b = ? a = x and b = 5 x3 + 3(x)2(5) + 3(x)(5)2 + (5)3 = x3 + 15x2 + 75x + 125

  13. 3x2 – x – 5 x + 2 3x3 + 5x2 – 7x – 10 Find the Product 3. (x + 2)(3x2 – x – 5) SOLUTION Multiply 3x2 – x – 5 by 2 . 6x2 – 2x – 10 3x3 – x2 – 5x Multiply 3x2 – x – 5 by x. Combine like terms.

  14. Multiply 4. (a – 5)(a + 2)(a + 6) SOLUTION (a – 5)(a + 2)(a + 6) = (a2 – 3a – 10)(a + 6) = (a2 – 3a – 10)a + (a2 – 3a – 10)6 = (a3 – 3a2 – 10a + 6a2 – 18a – 60) = (a3 + 3a2 – 28a – 60)

  15. Multiply 5. (xy – 4)3 a=? b=? a = xy b = 4 SOLUTION (a – b)3 = a3 - 3a2b + 3ab2 – b3 (xy – 4)3 = (xy)3 – 3(xy)2 + 3(xy)(4)2 – (4)3 = x3y3 – 12x2y2 + 48xy – 64

  16. Petroleum Since 1980, the number W(in thousands) of United States wells producing crude oil and the average daily oil output per well O(in barrels) can be modeled by W = – 0.575t2 + 10.9t + 548 andO = – 0.249t + 15.4 where tis the number of years since 1980. Write a model for the average total amount Tof crude oil produced per day. What was the average total amount of crude oil produced per day in 2000?

  17. What are the two ways that you can add, subtract or multiply polynomials? Horizontally or vertically • Name three special product patterns. Sum and difference, square of a binomial, and cube of a binomial (p.105).

  18. – 0.575t2 + 10.9t + 548 – 0.249t + 15.4 – 8.855t2 + 167.86t + 8439.2 0.143175t3 – 2.7141t2 – 136.452t 0.143175t3 – 11.5691t2 + 31.408t + 8439.2 SOLUTION To find a model for T, multiply the two given models. Total daily oil output can be modeled by T = 0.143t3–11.6t2 + 31.4t + 8440 where Tis measured in thousands of barrels. By substituting t = 20 into the model, you can estimate that the average total amount of crude oil produced per day in 2000 was about 5570 thousand barrels, or 5,570,000 barrels.

  19. 0.542t2 – 7.16t + 79.4 109t + 4010 2173.68t2 + 28711.6t + 318394 59.078t3 – 780.44t2 – 8654.6t 59.078t3 + 1392.98t2 – 20057t + 318394 Industry The models below give the average depth D(in feet) of new wells drilled and the average cost per foot C(in dollars) of drilling a new well. In both models, trepresents the number of years since 1980. Write a model for the average total cost T of drilling a new well. D = 109t + 4010 C = 0.542t2 – 7.16t + 79.4 To find a model for T, multiply the two given models. Total daily oil output

  20. 2.3 Assignment p. 107, 3-45 every third problem

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