Using the Quadratic Formula ALGEBRA 1 LESSON 10-7 pages 550–552  Exercises 1. –1, –1.5 2. 2.8, –6 3. 1.5 4. –0.67, –15 5. 6.67, –0.25 6. –4, –9 7. 2.67, –16 8. 13, –8.5 9. 16, –2.4 10. 0.07, –2.67 11. 10.42, 1.58 13. 1.14, –0.77 14. 2.20, –3.03 15. 3.84, –0.17 16. a. 0 = –16t 2 + 10t + 3 b. t 0.8; 0.8 s 17. a. 0 = –16t 2 + 50t + 3.5 b. t 3.2; 3.2 s 18. Completing the square or graphing; the x2 term is 1 but the equation is not factorable. 19. Factoring or square roots; the equation is easily factorable and there is no x term. 20. Quadratic formula; the equation cannot be factored. 21. Quadratic formula; the equation 22. Factoring; the equation is easily factorable. 10-7

Using the Quadratic Formula ALGEBRA 1 LESSON 10-7 34. About 2.1s 35. Answers may vary. Sample: You solve the linear equation using transformations and you solve the quadratic equation using the quadratic formula. 36. 7.40 ft and 5.40 ft 37. 13.44 cm and 7.44 cm 38. Answers may vary. Sample: A rectangle has length x. Its width is 5 feet longer than three times the length. Find the dimensions if its area is 182 ft2. 7 ft  26 ft 23. Quadratic formula; the equation cannot be factored. 24. 6, –6 25. 0.87, –1.54 26. 1.41, –1.41 27. 1.28, –2.61 28. 2 29. 3, –3 30. 1.72, –0.39 31. 1.4, –1 32. 2.23, –1.43 33. a. 7 ft  8 ft b. x(x + 1) = 60, 7.26 ft  8.26 ft 10-7

Using the Quadratic Formula ALGEBRA 1 LESSON 10-7 53. (6v – 5)(2v + 7) 54. (2x – 1)(3x – 5) 55. (5t + 3)(3t + 2) 39. if the expression b2 – 4ac equals zero 40. about 1.9 s 41. a. Check students’ work. b. 356.9 million c. 2007 42. a. s = – b. 6.5 46. [2] –1.8, 3.7 [1] correct substitution into quadratic formula, with one calculation error 47. 1.54, 8.46 48. –1, –2 49. 0.1, –6.1 50. (2c + 5)(c + 3) 51. (3z – 2)(z + 4) 52. (5n + 2)(n – 7) 11 ± (112) – 4(6)(–40) 2(6) x = a b 43. a. 7.62  107 lb b. 3.3  104 tons c. 6.27 s 44. D 45. F 10-7