139 1.4 Quadratic Equations CONCEPT PREVIEWUse Choices A–D to answer each question. A. 3x2 - 17x - 6 = 0 B. 12x + 522 = 7 C. x2 + x = 12 D. 13x - 121x - 72 = 0 9. Which equation is set up for direct use of the zero-factor property? Solve it. 10. Which equation is set up for direct use of the square root property? Solve it. 11. Only one of the equations does not require Step 1 of the method for completing the square described in this section. Which one is it? Solve it. 12. Only one of the equations is set up so that the values of a, b, and c can be determined immediately. Which one is it? Solve it. 1.4 Exercises CONCEPT PREVIEWMatch the equation in Column I with its solution(s) in Column II. I 1. x2 = 25 2. x2 = -25 3. x2 + 5 = 0 4. x2 - 5 = 0 5. x2 = -20 6. x2 = 20 7. x - 5 = 0 8. x + 5 = 0 II A. {5i B. {225 C. {i25 D. 5 E. {25 F. -5 G. {5 H. {2i25 Solve each equation using the zero-factor property. See Example 1. 13. x2 - 5x + 6 = 0 14. x2 + 2x - 8 = 0 15. 5x2 - 3x = 2 16. 2x2 - x = 15 17. -4x2 + x = -3 18. -6x2 + 7x = -10 19. x2 - 100 = 0 20. x2 - 64 = 0 21. 4x2 - 4x + 1 = 0 22. 9x2 - 12x + 4 = 0 23. 25x2 + 30x + 9 = 0 24. 36x2 + 60x + 25 = 0 Solve each equation using the square root property. See Example 2. 25. x2 = 16 26. x2 = 121 27. 27 - x2 = 0 28. 48 - x2 = 0 29. x2 = -81 30. x2 = -400 31. 13x - 122 = 12 32. 14x + 122 = 20 33. 1x + 522 = -3 34. 1x - 422 = -5 35. 15x - 322 = -3 36. 1-2x + 522 = -8 Solve each equation using completing the square. See Examples 3 and 4. 37. x2 - 4x + 3 = 0 38. x2 - 7x + 12 = 0 39. 2x2 - x - 28 = 0 40. 4x2 - 3x - 10 = 0 41. x2 - 2x - 2 = 0 42. x2 - 10x + 18 = 0 43. 2x2 + x = 10 44. 3x2 + 2x = 5 45. -2x2 + 4x + 3 = 0 46. -3x2 + 6x + 5 = 0 47. 4x2 - 8x + 7 = 0 48. 3x2 - 9x + 7 = 0 Concept Check Answer each question. 49. Francisco claimed that the equation x2 - 8x = 0 cannot be solved by the quadratic formula since there is no value for c. Is he correct?
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