Math 170 Diagnostic Test 3 Answers

1 INTERMEDIATE ALGEBRA READINESS DIAGNOSTIC TEST PRACTICE Directions: Study the examples, work the problems, then check your answers at the end of each topic. If you don’t get the answer given, check your work and look for mistakes. If you have trouble, ask a math teacher or someone else who understands this topic. TOPIC 1: ELEMENTARY OPERATIONS A. Algebraic operations, grouping, evaluation: To evaluate an expression, first calculate the powers, then multiply and divide in order from left to right, and finally add and subtract in order from left to right. Parentheses have preference. example: example: example: example: 14 − 3 = 14 − 9 = 5 2 • 4 + 3• 5 = 8 + 15 = 23 10 − 2 • 32 = 10 − 2 • 9 = 10 −18 = −8 (10 − 2) • 32 = 8 • 9 = 72 2 26. 3+ 6 = 3+ 9 6axy = 15by 2 19a = 95a 14 x−7y = 7y 27. 5a+b 5a+c 23. 24. 25. 23 = −24 = 4 + 2•5 = 32 − 2 • 3 + 1 = 5. 0 = 4 6. (− 2) = 5 7. 1 = example: 4 Problems 8-13: Find the value if a = − 3 , b = 2 , c = 0, d = 1, and e = − 3 : 8. a − e = 11. 9. e + (d − ab)c = 12. 2 10. a − (bc − d) + e = 13. 32. 3 •y x 15 2x 2 −x−1 x 2 −2x+1 • 10x = y2 3•10•x•y 15•x•y 2 y 3 5 2 x • • • • •1= 3 5 1 x y y 1 • 1 • 2 • 1 • 1 • 1y = 2y = = = + − = = b a 2d e 34. x 2 −3x x−4 • x (x−4 ) 2x−6 C. Laws of integer exponents: I. a b • a c = a b+c b II. aa c = a b−c = III. (a ) = a b c (ab) IV. V. example: 3x + y 2 − (x + 2y 2 ) (ab ) c bc c = ac • bc = ac bc VI. a = 1 (if a ≠ 0 ) VII. a− b = 1b a 0 = 3x − x + y − 2y = 2x − y 2 2 example: a − a + a = 2a − a 2 2 Problems 14-20: Simplify: 14. 15. 16. 17. 31. • yxy2 • 3y2 = 4x 6 Combine like terms when possible: 2 30. x− 4 = 4 −x 2( x+4 )(x−5) ( x−5)(x−4 ) x 2 −9x = x−9 8( x−1) 2 = 6( x 2 −1) Problems 33-34: Simplify: 33. e d b e d c 29. = Problems 1-7: Find the value: 1. 2. 3. 4. 28. 18. 3a − 2(4(a − 2b) − 3a ) = 19. 3(a + b) − 2(a − b) = 10r − 5(2r − 3y) = 20. 1+ x − 2x + 3x − 4 x = 6x + 3 − x − 7 = 2(3 − t) = x 2 − (x − x 2 ) = Problems 35-44: Find x: 35. 2 3 • 2 4 = 2 x 3 36. 24 = 2 x 40. 8 = 2 41. a x = a 3 • a 37. 3−4 = 42. 2 38. B. Simplifying fractional expressions: =5 52 52 1 3x x ( ) =2 4 3 x 43. x b 10 b5 1 c −4 = bx = cx a 3 y− 2 a 2 y− 3 = ax example: = = • = 1• = 4 (note that you must be able to find a common factor - in this case 9 - in both the top and bottom in order to reduce a fraction.) a example: 123ab = 33a•a•41b = 33aa • 41b = 1 • 41b = 41b (common factor: 3a) 39. 2 46. 3 = 47. 2 3 • 2 4 = 51. 2 x • 4 x −1 = c+ 3 52. 2 c−3 = Problems 21-32: Reduce: 48. 0 = 0 49. 5 = 53. 2 c +3 • 2 c −3 = x 54. 8x−1 = 27 36 21. 13 52 = 9• 3 9• 4 9 9 3 4 22. 3 4 3 Problems 45-59: Simplify: 45. 8x = 0 −4 5 26 65 = 44. 50. (−3) − 3 = 3 2 2 3 = 55. −3 2x 6 x −4 ( 58. − 2a = ( )= 56. a 57. x +3 x 3 x− 2 a a 2 x− 3 59. 2 ) (ab )= 2(4 xy ) (−2x y ) 2 4 2 2 −1 example: 2 −1 = = Problems 67-74: Write answer in scientific notation: −2 40 example: 32800 = 3.2800 ×10 if the zeros in the ten’s and one’s places are significant. If 4 the one’s zero is not, write 3.280 ×10 ; if 4 neither is significant: 3.28 ×10 −3 example: .004031 = 4.031× 10 2 example: 2 × 10 = 200 −1 example: 9.9 × 10 = .99 n Problems 60-63: Write in scientific notation: 69. 1.86×10 4 3×10 −1 = 73. 70. 3.6×10 −5 1.8×10 −8 = 74. 76. To compute with numbers written in scientific form, separate the parts, compute, and then recombine. ) 3.14 ×10 5 (2) = (3.14 ) (2) ×10 5 = 6.28 ×10 4.28×10 6 = 4.28 × −2 2.14 5 2.14×10 10 6 10 −2 Answers: 1. 8 2. –16 3. 14 4. 4 5. 0 6. 16 7. 1 8. 0 9. 9 10. –5 11. –3 12. − 2 3 13. no value (undefined) 14. 5 x − 4 15. 6 − 2t 16. 15 y 2 17. 2 x − x 18. a + 16b 19. a + 5b 20. 1 − 2 x 2 1 2 4 5 3 4 2ax 5b a 5 2x − y y 5a +b 5a +c 27. 28. -1 2(x + 4 ) 29. x − 4 30. x 4 (x −1) 31. 3(x +1) 32. 33. 34. 35. 36. 37. −1 (−2.92×10 )(4.1×10 ) 3 −8.2×10 −3 a a 7 = = 77. 3 + −3 = 78. 3 − −3 = Problems 79-84: If x = −4 , find: 79. x + 1 = 80. 1− x = 81. − x = 82. x + x = 83. −3 x = 84. ( x − ( x − x ) ) = = 2.00 ×10 8 21. 22. 23. 24. 25. 26. 2 example: 3 = 3 example: −3 = 3 example: a depends on a if a ≥ 0 , a = a 75. 0 = −6 66. 4 × 10 = ( = Problems 75-78: Find the value: Problems 64-66: Write in standard notation: 3 ( )= (2.5 ×10 ) = 72. 4 ×10−3 10 −40 10 −10 if a < 0 , a = −a example: − −3 = −3 62. 5.07 = 63. −32 = 64. 1.4030 × 10 = −2 65. −9.11×10 = = E. Absolute value: Note that scientific form always looks like a ×10 where 1 ≤ a < 10 , and n is an integer power of 10. 60. 93,000,000 = 61. .000042 = 1.8×10 −8 3.6×10 −5 71. 68. 4 example: = .250 ×10 3 = 2.50 ×10 2 67. 10 ×10 = D. Scientific notation: example: 2.01×10 −3 8.04×10 −6 2x +1 x−1 2 x2 x 2 7 –1 4 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 0 12 3 4 5 4 y +1 8 1 81 128 0 1 –54 2 3x −2 64 4c 2 2x +1 x 3 3 x 2 + 3x 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 56. a x +1 57. a 9 2 58. 16a b 2 59. x 3 60. 61. 62. 63. 64. 65. 9.3 ×10 7 4.2 ×10−5 5.07 –3.2 × 10 1403.0 -.0911 76. 1 if a > 0; -1 if a < 0; (no value if a = 0 ) 77. 6 78. 0 79. 3 80. 5 81. –4 82. 0 83. 12 84. 12 .000004 38 1× 10 1× 10−30 6.2 × 104 2.0 × 103 5.0 × 10−4 1.6 × 10−5 4.0 ×10−3 1.46 × 1013 0 TOPIC 2: RATIONAL EXPRESSIONS A. Adding and subtracting fractions: If denominators are the same, combine the numerators: example: 3x y − xy = 3x − x y = 2. 3. 4 7 + 27 = 3 x − x −3 = x −3 b−a − ab −+ ba = b+a 4. example: example: 5. 6 b = 5 ab ; 56a = bb • 56a = 56ab 5a 3x+2 = 4 (x+1) ; 3x+2 = 44 • 3x+2 x+1 x+1 x+1 x−1 = (x+1)(x−2) ; x+1 (x−2)(x−1) x−1 x 2 −3x+2 = (x−2)(x+1) = (x+1 x+1 )(x−2) 7. 8. 4 = 72 9 3x = 7y 7 x+3 = (x−1)(x+2) x+2 2 3( x+2) = 12x+8 4 x+4 9. 10. 2 3( x +2) = ax 6(x +1) = How to get the lowest common denominator (LCD) by finding the least common multiple (LCM) of all denominators: example: 5 6 and 8 15 . First find LCM of 6 and 15: 6 = 2• 3 15 = 3• 5 LCM = 2 • 3• 5 = 30 5 8 so, 6 = 25 , and 15 = 16 30 30 1 6a : and ax 6( x +1) 2•2(x +1) 2•3(x +1)(x +2) ax (x +2) 6(x +1)(x +2) 4 (x +1) = 6(x +1)(x +2) and Problems 11-16: Find equivalent fractions with the lowest common denominator: 12. 2 3 3 x and 5 13. x 3 and 11. and 2 9 14. 15. −4 x +1 16. 3 x −2 and 4 2− x 7x (y−1) x and 10(x−1) 15(x 2 −2) 2 1 3x , , and x x2 + x x x +1 After finding equivalent fractions with common denominators, proceed as before (combine numerators): − a4 = 24a − a4 = 3 1 example: x −1 + x +2 example: 30−15a = (1+b )(1−b ) 15−15b x −6 = −2 6− x and 3(x + 2) = 3• (x + 2) 6(x + 1) = 2 • 3• (x + 1) LCM = 2 • 3• (x + 1) • (x + 2) so, Problems 6-10: Complete: 6. example: 4 4 = 2•2 6a = 2 • 3• a LCM = 2 • 2 • 3• a = 12a 9a 2 so, 43 = 12a , and 6a1 = 12a 3y 2 x +2 − = 2 x +2 x xy 2 3a + b2 − ab = b If denominators are different, find equivalent fractions with common denominators: example: 3 4 is equivalent to how many eighths? 3 2•3 = 8 ; 43 = 1• 43 = 22 • 43 = 2•4 = 68 4 example: 3 2x y Problems 1-5: Find the sum or difference as indicated (reduce if possible): 1. example: a 2 3(x +2) 2a− a 4 = a 4 (x −1) = (x −1)(x +2) + (x −1)(x +2) x −1 = (3xx−1+6+ = 4 x +5 )(x +2) (x −1)(x +2) Problems 17-30: Find the sum or difference: 17. 18. 19. 20. 21. 22. − 21a = − a2 = − 2x = +2= −2= a − bc = 3 a 3 x 4 5 2 5 a b 23. 24. 25. 26. 27. + b1 = a − a1 = x + 1−x x = x −1 3x −2 2 − x +2 = x −2 2 x −1 2 x −1 − x −2 = x +1 1 a 4 28. (x −1)(x −2) + (x −2)(x −3) − (x −3)(x −1) = 1 29. 1 4 − x 2 −2 = x x x −2 7 7•6 = 2 1 = 42 = 42 1 = 42 1 − 2 (3 − 2 )• 6 4−3 5x 5x • 2y 5x 2y 5x example: 2y ÷ 2x = = 2y = = 5 2x 2x • 2y 4 xy 4 y 2 47. 3 = 39. 43 ÷ 23 = 2 x 30. x −2 − 4 x 2 −4 example: = B. Multiplying fractions: Multiply the top numbers, multiply the bottom numbers, and reduce if possible. 3 2 • = 4 5 3(x+1) • x−2 example: example: 31. 32. 2 3 • 3 8 a b 6 20 = 103 x 2 −4 x 2 −1 = 33. • dc = 34. (a+b ) (x−y ) ( p−5) 35. • (5− p) • (x−y ) 2 (a+b )2 36. 37. 3( x+1)(x+2)( x−2) = (x−2)(x+1)(x−1) = 3 () 3 2 4 2 ( ) 3 2a 5b 40. 11 83 ÷ 3x+6 x−1 = 38. 2 1 2 2 = = C. Dividing fractions: Make a compound fraction and then multiply the top and bottom (of the big fraction) by the LCD of both: example: a b ÷ dc = a b c d = a b c d • bd = • bd Answers: 1. 6 7 2. –1 3. 2b−2a b +a 4. − 2 x 5. 2ab+2 6. 32 7. 3xy 2 8. x + 2 x − 3 9. 2 + 2b − a − ab 10. 2 11. 69 , 29 12. 13. 14. 3 , 5xx x x (x +1) 3(x +1) , 22. 23. 27. 16. 17. 18. 2 x +1 , 3x x (x +1) x (x +1) 5 2a 3a−2x ax x −4 −3(2x−1) (x +1)(x−2) 28. 0 29. x +2 x 30. 2 31. 32. 2 33. ( ) 15. , 30(x −2)(x−1) 30(x −2)(x−1) 2 4 x−10 5x 12 5 a−2b b ab−c b a +b ab a 2 −1 a 24. 25. 0 2 26. 3x 2 +2x 3 , −4 x−2 x−2 21x (y−1) x 2 −2 , x(xx +1) = 48. 3 4 ÷2= 49. 42. a b ÷3= 50. 43. 3 a ÷ b3 = 51. 44. x+7 x 2 −9 1 x−3 = a−4 = 3 −2 a 2a − b 46. = 1 45. 4 2 3 4 a b c a = = = b c 1 − b1 a = 1 + b1 a 1 − b1 2a = 1 1 − a 2b 1 1 − a b = 1 ab 52. 53. 2 19. 20. 21. −12 3(x +1) 2x (x−1) ad bc 3 4 41. = ( ) = 3 2 • ab = 7a 12 3(x+4 ) 5y 3 • 5y x 2 −16 2 3 34. 35. x 2 +2x−4 x 2 −4 1 4 ac bd b 42 2 3y x−4 (a +b )(5− p ) x−y 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 9 16 8a 9 125b 3 25 4 9 8 91 6 3 8 a 3b 9 ab x +7 x +3 a 2 −4 a 3−2a 46. 4a − 2b 47. 8 3 48. 1 6 49. bca 50. 51. 52. ac b b−a b +a b−2a 2b−a 53. b − a 5 TOPIC 3: EXPONENTS and RADICALS A. Definitions of powers and roots: Problems 1-20: Find the value: Problems 44-47: Write given two ways: Given No negative No powers fraction d −4 44. 4 1. 2 = 11. 2. 3 = 12. −125 = 52 = 3. − 4 = 13. (−5) 4. (− 4) = 14. x2 = 46. 5. 0 = 4 6. 1 = 15. 16. a3 = 1 = 4 47. 3 2 2 2 4 7. 8. 3 64 = 17. 64 = 18. 9. 6 64 = 10. − 49 = 19. 20. 3 2 3 = 4 4 = a b • a c = a b +c ab ac =a III. (a ) = a IV. (ab) () a c b V. IV. = ac • bc = =5 52 52 ( ) 3 4 25. 2 26. 8 = 2 27. a 3 • a = a x x 28. 29. = 2x 30. b 10 b5 1 c −4 = cx 55. a 3 y −2 a 2 y −3 38. 2 • 4 c +3 39. x c−3 = 33. 2 3 • 2 4 = 40. 34. 0 = 41. 35. 5 = 36. (− 3) − 3 = 37. x c+3 •x 3 c− 3 = x−1 ( ) 43. = x +3 x − 3 3 x −2 a a 2 x −3 s r b 1 r r a ( ) = (a ) 1 1 s r 1 1 r s 51. x 2 = 1 52. 2 x 2 = 1 53. (2x ) 2 = = 3 5= 23 = 56. 3 a= = 1 a 57. 58. 4• 9= x 61. 59. x= 62. x = 3 60. x 8x = 2 x −1 −3 2x = 6 x −4 42. a 3 a= r s a r Problems 58-62: Find x: = ax 31. 7x = −4 32. 3 = 0 , or (a b ) r = 1 1 Problems 54-57: Write as a fractional power: 54. x 5 a b 48. 3 2 = 2 49. 4 3 = 1 50. (1 2) 3 = = bx Problems 31-43: Find the value: 0 a= r 1 Problems 21-30: Find x: 24. rs = 1 1 Problems 48-53: Write as a radical: a 1 3x x r a b r or a rs = a VI. a = 1 (if a ≠ 0 ) VII. a−b = 1b 23. 3−4 = p r 1 c a bc ( a) ab = r a • r b , or ( ab) r = a r • b r 1 0 21. 2 3 • 2 4 = 2 x 3 22. 224 = 2 x x 2 y 3 z −1 x 5 y −6 z −3 which is a real number. (Also true if r is a positive odd integer and a < 0 ) p power Think of r as root III. bc c 3 a 2 bc 2 ab 2 c p II. b−c b c −2 3x 3 y a ≥ 0 , then a r = r a p = 81a 8 = 7• 7 = B. Laws of integer exponents: I. II. ( ) ( ) 45. C. Laws of rational exponents, and radicals: Assume all radicals are real numbers: I. If r is a positive integer, p is an integer, and .04 = (23 ) d 4 9 3 64 = x 8 4 2 3 3 2 64 = x Problems 63-64: Write with positive exponents: ( 63. 9x 6 y −2 = ) 1 2 = ( 64. −8a 6b−12 D. Simplification of radicals: example: example: 3 32 = 16 • 2 = 4 2 72 = 3 8 • 3 9 = 23 9 ) − 23 = 6 54 + 4 16 = 27 • 3 2 + 4 3 8 • 3 2 = 33 2 + 4 • 2 3 2 = 33 2 + 8 3 2 = 113 2 example: 8 − 2 = 2 2 − 2 = 2 example: 3 3 81. 3 example: 65. − 81 = 73. x 2x + 2 2x + 50 = 67. 3 12 = 68. 3 54 = 69. 52 = 74. 3 2x 2 2x 71. x5 = 79. a2 = a3 = 3 5 a = 3 2+ 2= 5 3− 3= 9x2 − 9y2 = 72. 4x6 = 80. 9x2 + 9y 2 = 75. 76. 77. 70. 2 3 + 27 − 75 = 78. Answers: 1. 8 2. 9 3. –16 4. 16 5. 0 6. 1 7. 8 8. 4 9. 2 10. –7 11. –5 12. 5 13. 5 14. x if x ≥ 0 –x if x < 0 15. a 16. 1 2 17. 0.2 18. 16 81 2 19. 3a 20. 7 21. 7 22. –1 23. 4 24. 0 25. 12 26. 3 27. 4 28. 5 29. 4 30. y + 1 31. 7 2 82. 64 (x + y ) = 3 3 E. Rationalization of denominators: example: Problems 65-82: Simplify (assume all radicals are real numbers): 66. 9(x + y ) = 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. example: = 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. = 5 8 = 5 8 • Problems 83-91: Simplify: 83. 84. 85. 86. 87. 1 128 0 1 –54 x 2 3x −2 x6 2 2x +1 = 9−1 x −6 y 2 9x 6 a3 = 8−1 a 3 b−3 8b 3 y 9z 2 −3 9 2 =x y z x3 3 3 16 3 1 2 =3 4 2 x =x x 2 x 2x 1 52 3 22 1 a3 −1 a 2 36 3 4 9 1 = 5 3 = 3 a = b 3 2 = 3 2+ 88. 89. 90. 91. 64. 3 x 2 −9 d y2 = 63. 2c x 2 3 1 2 3 = 2 +1 3 = 1− 3 3+ 2 = 3− 2 60. 4 61. 2 62. 1 2 81 42. a x +1 43. a 44. 18 = d −8 45. 2 = 10 = 410 2 16 1 = 1 •3 4 = 3 4 = 3 4 3 3 3 2 2 2 3 4 8 3 3 3 +1 + 3 = • = 93−1 = 3+2 3 3−1 3−1 3 +1 5 8 65. 66. 67. 68. 69. 70. 71. 72. 3x 3 y b8 4a4 –9 5 2 6 3 33 2 2 13 0 x2 x 3 2x 73. 4 x 2x 74. a if a ≥ 0, -a if a < 0 75. a a 3 76. a a 2 77. 4 2 78. 4 3 79. 3 x 2 − y 2 80. 3 x 2 + y 2 81. 3 x + y 82. 4 (x + y ) 83. 84. 85. 6 5 3 5 3 = 7 86. 87. ab 3 18 3 2 88. 2 89. 3 2 − 3 b 3 90. 3 +3 −2 91. −7 − 4 3 TOPIC 4: LINEAR EQUATIONS and INEQUALITIES A. Solving one linear equation in one variable: Add or subtract the same value on each side of the equation, or multiply or divide each side by the same value, with the goal of placing the variable alone on one side. If there are one or more fractions, it may be desirable to eliminate them by multiplying both sides by the common denominator. If the equation is a proportion, you may wish to cross-multiply. Problems 1-15: Solve: 9. x − 4 = x2 + 1 1. 2 x = 9 2. 3 = 65x 3. 3x + 7 = 6 4. x3 = 45 10. 23xx+1 = 52 11. 6 − 4 x = x 12. 32xx−+21 = 4 6. x = x+3 2 x −1 =2 14. 7 x − 5 = 2 x + 10 15. 13 = x +x 8 5. 5 − x = 9 13. +1 7. 4 x − 6 = x 8. xx −+11 = 67 2x 5 To solve a linear equation for one variable in terms of the other, do the same as above: example: Solve for F: C = 5 9 (F − 32) = F − 32 Add 32: + 32 = F Thus, F = 95 C + 32 example: Solve for b: a + b = 90 Subtract a: b = 90 − a Multiply by 9 : 5 9 C 5 9 C 5 Problems 16-21: Solve for the indicated variable in terms of the other(s): 16. a + b = 180; b = 19. y = 3x − 2; x = 17. 2a + 2b =180; b = 20. y = 4 − x; x = 18. P = 2b + 2h; b = 21. y = 23 x + 1; x = B. Solving a pair of linear equations in two variables: The solution consists of an ordered pair, an infinite number of ordered pairs, or no solution. Problems 22-28: Solve for the common solution(s) by substitution or linear combinations: 22. x + 2y = 7 3x − y = 28 23. x+ y =5 x − y = −3 24. 2x − y = − 9 x =8 2x − y = 1 25. y = x −5 2 x − 3y = 5 26. 3x + 5 y = 1 4 x −1 = y 4x + y = 1 x+ y =3 28. x + y =1 2 x−y =3 29. 6x − 9 = 3y 27. C. Analytic geometry of one linear equation in two variables: The graph of y = mx + b is a line with slope m and y-intercept b. To draw the graph, find one point on it (such as (0, b)) and then use the slope to find another point. Draw the line joining the two points. example: y = −23 x + 5 has slope −3 2 and y-intercept 5. To graph the line, locate (0, 5). From that point, go down 3 (top of slope fraction), and over (right) 2 (bottom of fraction) to find a second point. Draw the line joining the points. Problems 30-34: Find slope and y-intercept, and sketch the graph: 30. y = x + 4 31. y = − 12 x − 3 32. 2 y = 4 x − 8 33. x − y = −1 34. x = −3 y + 2 A vertical line has no slope, and its equation can be written so it looks like x = k (where k is a number). A horizontal line has zero slope, and its equation looks like y = k . example: Graph on the same graph: x + 3 = −1 and 1 + y = −3 . The first equation is x = −4 The second is y = −4 Problems 35-36: Graph and write an equation for… 35. The line through (-1, 4) and (-1, 2) 36. The horizontal line through (4, -1) 8 D. Analytic geometry of two linear equations in two variables: Two distinct lines in a plane are either parallel or intersecting. They are parallel if and only if they have the same slope, and hence the equations of the lines have no common solutions. If the lines have unequal slopes, they intersect in one point and their equations have exactly one common solution. (They are perpendicular if and only if their slopes are negative reciprocals, or one is horizontal and the other is vertical.) If one equation is a multiple of the other, each equation has the same graph, and every solution of one equation is a solution of the other. Problems 37-44: For each pair of equations in problems 22 to 29, tell whether the lines are parallel, perpendicular, intersecting but not perpendicular, or the same line: 37. 38. 39. 40. Problem 22 Problem 23 Problem 24 Problem 25 41. 42. 43. 44. E. Solution of a one-variable equation reducible to a linear equation: Some equations which do not appear to be linear can be solved by using a related linear equation: example: 3 − x = 2 Since the absolute value of both 2 and –2 is 2, 3-x can be either 2 or –2. Write these two equations and solve each: 3− x = 2 3 − x = −2 or −x = −5 −x = −1 x =1 x =5 Problems 45-49: Solve: 48. 2 − 3x = 0 46. x = −1 49. x + 2 = 1 Problems 50-52: Solve and check: 3− x = 4 52. 3 = 3x − 2 2x + 1 = x − 3 50. 51. if a > b, then : a+c >b+c a−c >b−c ac > bc (if c > 0) ac < bc (if c < 0) a c a c > < b c b c (if c > 0) (if c < 0) if a < b, then : a+c 0) ac > bc (if c < 0) a c a c < > b c b c (if c > 0) (if c < 0) example: One variable graph: solve and graph on a number line: 1− 2x ≤ 7 (This is an abbreviation for {x: 1 − 2x ≤ 7 }) Subtract 1, get − 2 x ≤ 6 Divide by –2, x ≥ −3 Graph: -4 -3 -2 -1 0 1 2 3 53. 54. 55. 56. 2x −1 = 5 Answers: 1. 9 2 2. 5 2 3. − 1 3 4. 15 4 5. – 4 6. 5 3 7. 2 8. 13 Be sure to check answer(s): 2x − 1 = 2 •13 − 1 = 25 = 5 (Check) example: x = −3 Square: x =9 Check: x = 9 = 3 ≠ −3 There is no solution, since 9 doesn’t satisfy the original equation (it is false that 9 = −3). Problems 53-59: Solve and graph on a number line: 47. x − 1 = 3 example: Solve: F. Linear inequalities: Rules for inequalities: Problem 26 Problem 27 Problem 28 Problem 29 45. x = 3 2 x −1 = 25 2 x = 26 x = 13 Square both sides: 9. 10. 11. 12. 13. 14. 15. 16. 10 − 54 6 5 − 65 5 3 3 4 180 − a x −3> 4 4x < 2 2x + 1≤ 6 3< x −3 57. 4 − 2x < 6 58. 5 − x > x − 3 59. x > 1 + 4 17. 90 − a 18. P 2 − h = 19. (y + 2)3 20. 4 − y 21. 3(y −1)2 22. (9, -1) 23. (1, 4) p− 2h 2 9 33. m = 1, b = 1 24. (8, 25) 25. (-4, -9) 26. (2819 , − 1319) 34. m = −1 3 , b = 2 3 27. (1 4 , 0) 28. no solution 29. (a, 2a − 3), where a is any number; infinite number of solutions 30. m = 1, b = 4 4 31. m = −1 2, 35. x = −1 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 1 2 3 -1 36. y = −1 -1 37. 38. 39. 40. 41. 42. 43. 44. b = −3 -3 32. m = 2, b = −4 -4 intersecting, not ⊥ ⊥ intersecting, not ⊥ intersecting, not ⊥ intersecting, not ⊥ intersecting, not ⊥ parallel same line –3, 3 no solution –2, 4 2 3 –3, -1 –13 no solution in real numbers 11 3 x>7 0 x< 2 x ≤ 52 7 1 x>6 x > −1 x<4 x>5 0 1 0 2 3 0 6 -1 0 0 0 4 5 TOPIC 5: QUADRATIC POLYNOMIALS, EQUATIONS, and INEQUALITIES example: x − 6x + 9 = (x − 3) A. Multiplying polynomials: example: example: example: example: example: example: example: 2 (x + 2) (x + 3) = x 2 + 5x + 6 (2x −1) (x + 2) = 2x 2 + 3x − 2 (x − 5) (x + 5) = x 2 − 25 −4 (x − 3) = −4 x + 12 (x + 2) (x 2 − 2x + 4)= x 3 + 8 2 (3x − 4) = 9x 2 − 24 x +16 (x + 3) (a − 5) = ax − 5 x + 3a −15 Trinomial: example: x 2 − x − 2 = (x − 2) (x + 1) example: 6x 2 − 7x − 3 = (3x + 1) (2x − 3) Sum and difference of two cubes: a 3 + b 3 = (a + b) a 2 − ab + b 2 a −b 3 2. 3. 4. 5. (x + 3) = 2 (x − 3) = (x + 3)(x − 3) = (2 x + 3)(2 x − 3) = (x − 4 )(x − 2) = 2 6. −6x (3 − x ) = ( 9. ) 10. (x − 12 ) = 2 (x −1)(x + 3) = (x 2 )( ) −1 x 2 + 3 = B. Factoring: Monomial factors: ab + ac = a(b + c ) example: x 2 − x = x (x − 1) 11. 12. 13. 14. 15. 16. 17. 18. 19. example: 4 x y + 6 xy = 2 xy (2 x + 3) 2 Difference of two squares: a − b = (a + b)(a − b) 2 2 example: 9 x − 4 = (3 x + 2)(3 x − 2) 2 Trinomial square: a 2 + 2 ab + b 2 = (a + b) 2 a 2 − 2ab + b 2 = (a − b) 2 ( = (a − b) (a 2 ) + ab + b ) 2 ( Problems 11-27: Factor: 7. (2 x − 1) 4 x 2 + 2 x + 1 = 8. 3 ) example: x 3 − 64 = x 3 − 4 3 = (x − 4 ) x 2 + 4 x + 16 Problems 1-10: Multiply: 1. 2 a 2 + ab = a 3 − a 2b + ab 2 = 8x2 − 2 = x 2 −10 x + 25 = −4 xy + 10 x 2 = 2 x 2 − 3x − 5 = x2 − x − 6 = x2y − y2x = 8x 3 + 1 = 20. 21. 22. 23. 24. x 2 − 3 x − 10 = 2x 2 − x = 8x 3 + 8x 2 + 2x = 9 x 2 + 12 x + 4 = 6 x 3y 2 − 9 x 4 y = 25. 1− x − 2 x 2 = 26. 3 x 2 − 10 x + 3 = 27. x 4 + 3 x 2 − 4 = C. Solving quadratic equations by factoring: If ab = 0 , then a = 0 or b = 0 . example: if (3 − x )(x + 2) = 0 then (3 − x ) = 0 or (x + 2) = 0 and thus, x = 3 or x = −2 Note: there must be a zero on one side of the equation to solve by the factoring method. 10 example: 6x = 3x Rewrite: 6x 2 − 3x = 0 Factor: 3x (2x −1) = 0 So 3x = 0 or (2x −1) = 0 Thus x = 0 or x = 1 2 2 F. Quadratic inequalities: 2 Problems 28-39: Solve by factoring: 28. x (x − 3) = 0 34. 29. x − 2x = 0 35. (x + 2)(x − 3) = 0 (2 x + 1)(3 x − 2) = 0 36. 37. 38. 39. 6 x2 = x + 2 9 + x 2 = 6x 1− x = 2 x 2 x2 − x −6 = 0 2 30. 31. 32. 33. 2x = x 3x (x + 4 ) = 0 x2 = 2− x x2 + x = 6 2 x x < −2 D. Completing the square: x 2 + bx will be the square of a binomial when c is added, if c is found as follows: find half the x coefficient and square it–this is c. Thus, c = (b2 ) 2 = b2 4 x + bx + c = x + bx + 2 2 b 4 = (x + ) b 2 2 example: x + 5x 2 Half of 5 is 5 2 , and (5 2) = 25 4 , which must be added to complete the square: 2 25 4 = (x + ) 5 2 2 2 If the coefficient of x is not 1, factor it so that it is. Half of − 1 3 is − 1 6 , and (− 1 6) = 2 (x − x + )= (x − ) , and 3(x − x + )= 3x − x + 1 3 2 Thus 3 36 1 3 (or 1 36 1 36 1 must 12 ) 1 2 6 2 1 36 , so 3 36 be added to 3x − x to 2 complete the square. Problems 40-43: Complete the square, and tell what must be added: 40. x − 10x 2 41. x + x 2 42. x 2 − 23 x 43. 2 x + 8 x 2 E. The quadratic formula: 2 If a quadratic equation looks like ax + bx + c = 0 , then the roots (solutions) can be found by using the quadratic formula: x = − b ± b 2 − 4 ac 2a Problems 44-49: Solve: 44. x − x − 6 = 0 2 45. x + 2x = −1 2 46. 2x − x − 2 = 0 2 neg neg pos Solution ? neg pos pos pos no neg yes −2 < x < 3 pos no x>3 Therefore, if (x − 3)( x + 2) < 0 , then −2 < x < 3 Note that this solution means that x > −2 and x < 3 50. x − x − 6 > 0 2 51. x + 2 x < 0 2 52. x − 2x < −1 2 G. Complex numbers: −1 is defined to be i, so i 2 = −1 example: i 3 = i 2 • i = −1 • i = −i 4 A complex number is of the form a + bi , where a and b are real numbers. a is called the real part and b is the imaginary part. If b is zero, a + bi is a real number. If a = 0 , then a + bi is pure imaginary. Complex number operations: example: (3 + i ) + (2 − 3i ) = 5 − 2i example: (3 + i ) − (2 − 3i ) = 1 + 4i 2 example: (3 + i)(2 − 3i) = 6 − 7i − 3i = 6 − 7i + 3 = 9 − 7i example: = 23−+3ii • 22++ 33ii = 6+411+i9− 3 = 3+1311i = 133 + 11 i 13 3+ i 2− 3i Problems 56-65: Write each of the following so the answer is a+bi: 6 56. (3 + 2i) (3 − 2i) = 61. i = 7 57. (3+ 2i )+ (3− 2i ) = 62. i = 58. (3+ 2i )− (3− 2i ) = 59. (3+ 2i )÷ (3− 2i ) = 60. i = 5 47. x − 3x − 4 = 0 2 48. x + x − 5 = 0 2 49. x + x = 1 2 53. x > x 2 54. 2 x + x −1 > 0 2 55. Find the value of i . example: 3x 2 − x = 3(x 2 − 13 x) 2 (x − 3) (x + 2) (x − 3) × (x + 2) Problems 50-54: Solve, and graph on a number line: , and 2 x 2 + 5x + example: Solve x − x < 6 . First make one side 2 zero: x − x − 6 < 0 Factor: (x − 3)(x + 2) < 0 . If (x − 3) = 0 or (x + 2) = 0 then x = 3 or x = −2 . These two numbers (3 and –2) split the real numbers into three sets (visualize the number line): 63. i = 8 1991 64. i 65. 1 i = = Problems 66-67: Solve and write the answer as a+bi: 66. x + 2 x + 5 = 0 2 67. x + x + 2 = 0 2 11 Answers: 1. x 2 + 6 x + 9 2. x 2 − 6x + 9 3. x 2 − 9 4. 4 x 2 − 9 5. x 2 − 6x + 8 6. −18 x + 6 x 2 7. 8 x 3 − 1 8. x 2 − x + 14 9. x 2 + 2x − 3 10. x 4 + 2x 2 − 3 11. a (a + b) ( 24. 3 x 3 y (2 y − 3 x ) 25. (1− 2x ) (1+ x ) 26. (3 x − 1) (x − 3) 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. ) 12. a a − ab + b 13. 2(2 x + 1) (2 x − 1) 2 2 14. (x − 5) 15. 2x (−2y + 5x ) 2 16. (2 x − 5) (x + 1) 17. 18. 19. 20. 21. (x − 3)(x + 2) 2 ) + 4 (x + 1) (x − 1) 2 42. (x − 43 ) , add 2 ) 43. 44. 45. 46. 47. 22. 2x (2x + 1) 2 23. (3x + 2) 2 -2 0 1 9 3 51. −2 < x < 0 0, 3 0, 2 0, 1 2 –4, 0 –2, 1 –3, 2 –2, 3 − 12 , 2 3 − 12 , 2 3 3 –1, 1 2 –2, 3 2 (x − 5) , add 25 41. (x + 12 ) , add xy ( x − y ) (2 x +1) 4 x 2 − 2 x + 1 (x − 5)(x + 2) x (2 x − 1) ( (x 48. −1±2 21 49. −1±2 5 50. x < −2 or x > 3 0 -2 52. no solution, no graph 53. 0 < x < 1 0 1 54. x < −1 or x > 1 2 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 4 16 2(x + 2) , add 8 –2, 3 –1 2 1± 17 4 1 13 6 4i 5 13 + 12 i 13 i –1 –i 1 –i –i −1 ± 2i − 12 ± 27 i –1, 4 TOPIC 6: GRAPHING and the COORDINATE PLANE A. Graphing points: 1. Join the following points in the given order: (-3, -2), (1, -4), (3, 0), (2, 3), (-1, 2), (3, 0), (-3, -2), (-1, 2), (1, -4) example: A(3, -1), B(-2, 4) AB = (4 − (−1)) + (−2 − 3)2 = 2 5 2 + (−5) = 50 = 25 2 = 5 2 2 Problems 7-10: Find the length of the segment joining the given points: 2. In what quadrant does the point (a, b) lie, if a > 0 and b < 0 ? Problems 3-6: For each given point, which of its coordinates, x or y, is larger? 5 6 4 7. (4, 0), (0, -3) 8. (-1, 2), (-1, 5) 9. (2, -4), (0, 1) 10. − 3, − 5 , 3 3, − 6 ( )( C. Linear equations in two variables, slope, intercepts, and graphing: The line joining the points P1 (x1, y1 ) and P2 (x 2 , y 2 ) has slope y 2 − y1 x 2 − x1 . example: A(3,-1), B(-2,4) slope of 3 B. Distance between points: The distance between the points P1 (x1, y1 ) and P2 (x 2 , y 2 ) is found by using the Pythagorean Theorem, which gives P1P2 = (x 2 − x1 ) 2 + (y 2 − y1 ) . 2 ____ AB = 4 −(−1) −2− 3 = −55 = −1 Problems 11-15: Find the slope of the line joining the given points: 11. (-3, 1), and (-1, -4) 13. (3, -1), and (5, -1) 12. (0, 2), and (-3, 5) ) 12 14. 15. To find the x-intercept (x-axis crossing) of an equation, let y be zero and solve for x. For the yintercept, let x be zero and solve for y. example: 3y − 4 x = 12 if x = 0 , y = 4 so y-intercept is 4. If y = 0 , x = −3 so xintercept is –3. The graph of y = mx + b is a line with slope m and y-intercept b. To draw the graph, find one point on it (such as (0, b)) and then use the slope to find another point. Draw the line joining the two. example: y = −23 x + 5 has slope − 3 2 and yintercept 5. To graph the line, locate (0, 5). From that point, go down 3 (top of slope fraction), and over (right) 2 (bottom of fraction) to find a second point. Join. Problems 21-25: Find an equation of the line: 21. Through (-3, 1) and (-1, -4) 22. Through (0, -2) and (-3, -5) 23. Through (3, -1) and (5, -1) 24. Through (8, 0), with slope –1 25. Through (0, -5), with slope 2 3 A vertical line has no slope, and its equation can be written so it looks like x = k (where k is a number). A horizontal line has zero slope, and its equation looks like y = k . example: Graph on the same graph: x + 3 = −1 and 1 + y = −3 . The first equation is x = −4 ; the second is y = −4 . Problems 26-27: Graph and write equation for: 26. The line through (-1, 4) and (-1, 2) 27. Horizontal line through (4, -1) D. Linear inequalities in two variables: example: Two variable graph: graph solution on a number plane: x − y > 3 (This is an abbreviation for { (x, y ): x − y > 3 }. Subtract x, multiply by –1, get y < x − 3 . Graph y = x − 3 , but draw a dotted line, and shade the side where y < x − 3 : 28. y < 3 29. y > x 30. y ≥ 23 x + 2 Problems 16-20: Find the slope and y-intercept, and sketch the graph: 16. y = x + 4 17. y = − 12 x − 3 18. 2 y = 4 x − 8 19. x − y = − 1 20. x = −3 y + 2 To find an equation of a non-vertical line, it is necessary to know its slope and one of its points. Write the slope of the line through (x, y ) and the known point, then write an equation which says that this slope equals the known slope. example: Find an equation of the line through (-4, 1) and (-2, 0). Slope = −14−+02 = −12 Using (-2, 0) and (x, y ), y−0 Slope = x + 2 = −12 ; cross multiply, get −2y = x + 2, or y = − 12 x −1 31. x < y + 1 32. x + y < 3 33. 2 x − y > 1 E. Graphing quadratic equations: 2 The graph of y = ax + bx + c is a parabola, opening upward (if a > 0 ) or downward (if a < 0 ), and with line of symmetry. x = −2 ba , also called axis of symmetry. To find the vertex V(h, k) of the parabola, h = −2 ba (since V is on the axis of symmetry), and k is the value of y when h is substituted for x. example: y = x − 6 x 2 a = 1, b = −6, c = 0 x = −b = 62 = 3 2a Axis: h = 3, k = 32 −18 = −9 Thus, vertex is (3, − 9) 13 example: y = 3 − x V(0, 3), 2 Axis: x = 0 , y-intercept: if x = 0 , y = 3 − 0 = 3 2 x-intercept: if y = 0 , 0 = 3 − x , Problems 34-40: Sketch the graph: 2 34. y = x 35. y = − x so 3 = x , and x = ± 3 2 38. y = (x + 1) 2 2 36. y = x + 1 2 2 39. y = (x − 2) −1 2 40. y = (x + 2)(x − 1) 37. y = x − 3 2 Answers: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 21. 22. 23. 24. 25. 26. IV x y y x 5 3 29 7 − 52 -1 0 − 35 3 y = − 5 2 x − 13 2 32. y = 23 x − 5 33. y= x−2 y = −1 y = −x + 8 x = −1 -1 27. y = −1 -1 28. 29. 34. 35. 36. 1 37. 4 m = 1, b = 4 4 30. 38. 17. m = − 1 2 , b = −3 -1 -3 39. 18. m = 2, b = −4 (2,-1) 31. -4 19. m = 1, b = 1 40. 1 -2 20. m = − 1 3 , b = 2 3 1 2 3 TOPIC 7: LOGARITHMS and FUNCTIONS A. Functions: The area A of a square depends on its side length s, and we say A is a function of s, and write ‘A = f (s )’; for short, we read this as ‘A = f of s.’ There are many functions of s. 2 2 The one here is s . We write this f (s) = s and can translate: ‘the function of s we’re talking 2 2 about is s ’. Sometimes we write A (s ) = s . This says the area A is a function of s, and 2 specifically, it is s . B. Function values and substitution: 2 If A (s ) = s , A(3), read ‘A of 3’, means replace 2 every s in A (s) = s with 3, and find A when s is 3. 2 When we do this, we find A (3) = 3 = 9 . example: g(x ) is given: y = g(x ) = πx 2 14 example: g(3) = π • 3 = 9π Problems 24-28: For this graph, tell whether the statement is true or false: 2 example: g(7) = π • 7 2 = 49π example: g(a) = πa 2 example: g(x + h ) = π(x + h ) = πx 2 + 2πxh + πh 2 2 1. Given y = f (x ) = 3x − 2 . Complete these ordered pairs: (3,___), (0,___), ( 1 2 ,___), (___, 10), (___,-1) ( x − 1, ___) Problems 2-10: Given f (x ) = x − 4x + 2 . Find: 2 2. f (0) = 3. f (1) = 4. f (−1) = 5. f (−x ) = 6. − f (x ) = 7. f (x ) − 2 = 8. f (x − 2) = 9. 2 f (x ) = 10. f (2x ) = Problems 11-15: Given f (x ) = x . x+1 Find: 14. f (−1) = 15. f (x −1) = 11. f (1) = 12. f (−2) = 13. f (0) = example: If k(x ) = x − 4x , for what x is k(x ) = 0 ? 2 If k(x ) = 0 , then x − 4 x = 0 and since 2 x − 4x = x (x − 4) = 0 , x can be either 0 or 4. 2 (These values of x: 0 and 4, are called ‘zeros of the function’, because each makes the function zero.) Problems 16-19: Find all real zeros of: 16. x (x + 1) 17. 2x 2 − x − 3 27. g(−2) > g(1) 28. g(2) < g(0) < g(4) 24. g(−1) = g(0) 25. g(0) = g(3) 26. g(1) > g(−1) C. Logarithms and exponents: Exponential form: 2 = 8 Logarithmic form: log 2 8 = 3 3 Both of the equations above say the same thing. ‘ log 2 8 = 3 ’ is read ‘log base two of eight equals three’ and translates ‘the power of 2 which gives 8 is 3’. Problems 29-32: Write the following information in both exponential and logarithmic forms: 29. The power of 3 which gives 9 is 2. 3 30. The power of x which gives x is 3 1 31. 10 to the power –2 is 100 . 32. 12 is the power of 169 which gives 13. Problems 33-38: Write in logarithmic form: 1 36. 10 = 10−1 37. a b = c 38. y = 3x 33. 4 3 = 64 34. 30 =1 35. 25 = 5 2 Problems 39-44: Write in exponential form: 39. log3 9 = 2 40. log3 1 = 0 41. 5 = log 2 32 42. 1 = log4 4 43. y = loga x 44. logb a = 2 Problems 45-50: Find the value: 48. 6310 = 49. log 49 7 = 50. log 7 49 = 18. x −16x + 64 19. x 2 + x + 2 2 Problems 20-23: Given f (x ) = x − 4x + 2 , 45. 210 = 46. log 4 410 = 47. log 6 6 = find real x so that: D. Logarithm and exponent rules: exponent rules: log rules: all quantities real) (base any positive real number except 1) 20. f (x ) = −2 21. f (x ) = 2 2 22. f (x ) = −3 23. x is a zero of f (x ) Since y = f (x ), the values of y are the values of the function which correspond to specific values of x. The heights of the graph above (or below) the x-axis are the values of y and so also of the function. Thus for this graph, f (3) is the height (value) of the function at x = 3 and the value is 2: At x = −3 , the value (height) of f (x ) is zero; in other words, f (−3) = 0 . Note that f (3) > f (−3) , since 2 > 0 , and that f (0) < f (−1), since f (−1) = 1 and f (0) < 1. 10 ab • ac = ab+c ab = a b−c ac (a ) = a b c log ab = log a + log b log ab = log a − log b log a b = b log a bc (ab) c = acbc c c (ab ) = ab c a 0 = 1 (if a ≠ 0) a− b = a1b p log a a b = b a(log a b ) = b log b loga b = log c a c ( ) p ar = r ap = r a (think of rp as power ) (base change rule) root 15 Problems 51-52: Given log 2 1024 =10 , find: 51. log 2 1024 5 = 52. log 2 1024 = Problems 53-63: Solve for x in terms of y and z: 53. 3x = 3y • 3z 55. x 3 = y 54. 9 y = 56. 3x = y 57. 58. 59. 60. 61. 62. 63. 3z 3x log 7 3 = y; log 7 2 = z; x = log 3 2 y = loga 9; x = log a 3 64. 6 2 x = 6 3 65. 2 2 x = 2 3 74. 5 x +1 = 1 70. 4 3 • 4 5 = 4 x 75. log 3 37 = x 77. 78. 79. 80. 81. log10 x = log10 4 + log10 2 log 3 2 x = log 3 8 + log 3 4 − 4 log 3 2 log x 25 = 2 3log a 4 = log a x log(2 x − 6) = log(6 − x ) 82. log x 3 log x 4 84. = log 4 3 ) 88. log 4 64 = x log 3 81 81 − log 3 27 log 3 27 86. log 2 1 32 =x 87. log16 x = 29. 32 = 9, log 3 9 = 2 30. x 3 = x 3 , log x x 3 = 3 31. 10−2 = 1100 , log10 1100 = −2 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 169 = 13, log169 13 = 1 2 log 4 64 = 3 log 3 1 = 0 log 5 25 = 2 log10 110 = −1 log a c = b log 3 y = x 32 = 9 30 = 1 2 5 = 32 41 = 4 ay = x b2 = a 1024 10 1 2 = 1024 10 1 2 2 50 5 4 89. 5 = 5x = x 90. 27 x = (19 ) 85. log 4 3 30 = x log 4 30 91. 4 10 = 2 x 1/ 2 y+z z − 2y x 76. 6(log 6 x ) = 8 ( 66. 4 x = 8 67. 9 x = 27 x −1 Answers: 1. 7, -2, − 1 2 , 4, 1 3 , 3x − 5 2. 2 3. –1 4. 7 2 5. x + 4 x + 2 2 6. −x + 4x − 2 2 7. x − 4x 2 8. x − 8x + 14 2 9. 2x − 8x + 4 2 10. 4x − 8x + 2 11. 1 2 12. 2 13. 0 14. no value 15. xx−1 16. –1, 0 17. –1, 3 2 18. 8 19. none 20. 2 21. 0, 4 22. none 23. 2 ± 2 24. F 25. T 26. T 27. T 28. T 69. log 3 4 x = log 3 6 83. log 3 27 • 3−4 = x E. Logarithmic and exponential equations: Problems 64-93: Use the exponent and log rules to find the value of x: 3 73. 5 2 71. 3−2 = x x 72. 33 = 30 log x 2 = 3log y log x = 2log y − log z 3log x = log y log x = log y + log z log x + log 3 y = log z 2 ( ) =5 68. log 3 x = log 3 6 3 2 92. 2 x = 3 93. 3 • 2 x = 4 55. y 3 = 3 y 56. log 3 y 1 57. y 2 = y y 3 58. y2 z 3 59. y 60. yz 61. z4 3 62. z 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. y y2 y 2 3 3 3 2 2 2 3 6 3 2 8 1 9 1 6 –1 7 8 8 1 5 3 16 80. 64 81. 4 82. any real number > 0 and ≠ 1 83. –1 84. 1 3 85. 86. 87. 88. 89. 90. 1 91. 20 3 92. log log 2 3 –5 64 3 1 93. log 4 − log 3 log 2 (any base; if base=2, x = 2 − log 2 3) 4 –2 TOPIC 8: WORD PROBLEMS of 1 6 of 3 4 of a number is 12. What is the number? 2. On the number line, points P and Q and 2 units apart. Q has coordinate x. What are the possible coordinates of P? 3. What is the number, which when multiplied by 32, gives 32 • 46? 2 4. If you square a certain number, you get 9 . What is the number? 1 5. What is the power of 36 that gives 36 2 ? 6. Point X is on each of two given intersecting lines. How many such points X are there? 7. Point Y is on each of two given circles. How many such points Y? 8. Point Z is on each of a given circle and a given ellipse. How many such Z? 9. Point R is on the coordinate plane so its distance from a given point A is less than 4. Show in a sketch where R could be. 1. 2 3 Problems 10-11: B C O A 10. If the length of chord AB is x and length of CB is 16, what is AC? 11. If AC = y and CB = z , how long is AB (in terms of y and z)? 12. This square is cut into two smaller squares and two non-square rectangles as shown. a Problems 15-16: x and y are numbers, and two x’s equal three y’s. 15. Which of x or y must be larger? 16. What is the ratio of x to y? Problems 17-21: A plane has a certain speed in still air. In still air, it goes 1350 miles in 3 hours: 17. What is its (still air) speed? 18. How long does it take to fly 2000 miles? 19. How far does the plane go in x hours? 20. If the plane flies against a 50 mph headwind, what is its ground speed? 21. If it has fuel for 7.5 hours of flying time, how far can it go against this headwind? Problems 22-32: Georgie and Porgie bake pies. Georgie can complete 30 pies an hour: 22. 23. 24. 25. How many can he make in one minute? How many can he make in 10 minutes? How many can he make in x minutes? How long does he take to make 200 pies? Problems 26-28: Porgie can finish 45 pies an hour: 26. How many can she make in one minute? 27. How many can she make in 20 minutes? 28. How many can she make in x minutes? b a b Before being cut, the large square had area (a + b)2 . The two smaller squares have areas a2 and b 2 . Find the total area of the two nonsquare rectangles. Do the areas of the 4 parts add up to the area of the original square? 13. Find x and y: 14. When constructing an equilateral triangle with an area that is 100 times the area of a given equilateral triangle, what length should be used for a side? Problems 29-32: If they work together, how many pies can they produce in: 29. 1 minute 30. x minutes 31. 80 minutes 32. 3 hours Problems 33-41: A nurse needs to mix some alcohol solutions, given as a percent by weight of alcohol in water. Thus in a 3% solution, 3% of the weight would be alcohol. She mixes x grams of 3% solution, y grams of 10% solution, and 10 grams of pure water to get a total of 140 grams of a solution which is 8% alcohol: 17 33. In terms of x, how many grams of alcohol are in the 3% solution? 34. The y grams of 10% solution would include how many grams of alcohol? 35. How many grams of solution are in the final mix (the 8% solution)? 36. Write an expression in terms of x and y for the total number of grams in the 8% solution contributed by the three ingredients (the 3%, 10%, and water). 37. Use your last two answers to write a ‘total grams equation’. 38. How many grams of alcohol are in the 8%? 39. Write an expression in terms of x and y for the total number of grams of alcohol in the final solution. 40. Use the last two answers to write a ‘total grams of alcohol equation’. 41. How many grams of each solution are needed? 42. Half the square of a number is 18. What is the number? 43. If the square of twice a number is 81, what is the number? 44. Given a positive number x. The square of a positive number y is at least 4 times x. How small can y be? 45. Twice the square of half of a number is x. What is the number? Problems 46-48: Half of x is the same as onethird of y: 46. Which of x and y is the larger? 47. Write the ratio x : y as the ratio of two integers. 48. How many x’s equal 30 y’s? Problems 49-50: A gathering has twice as many women as men. If W is the number of women and M is the number of men: 49. Which is correct: 2M=W or M=2W? 50. If there are 12 women, how many men are there? Problems 51-53: If A is increased by 25%, it equals B: 51. Which is larger, B or the original A? 52. B is what percent of A? 53. A is what percent of B? Problems 54-56: If C is decreased by 40%, it equals D: 54. Which is larger, D or the original C? 55. C is what percent of D? 56. D is what percent of C? Problems 57-58: The length of a rectangle is increased by 25% and its width is decreased by 40%: 57. Its new area is what percent of its old area? 58. By what percent has the old area increased or decreased? Problems 59-61: Your wage is increased by 20%, then the new amount is cut by 20% (of the new amount): 59. Will this result in a wage which is higher than, lower than, or the same as the original wage? 60. What percent of the original wage is this final wage? 61. If the above steps were reversed (20% cut followed by 20% increase), the final wage would be what percent of the original wage? 62. Find 3% of 36. 63. 55 is what percent of 88? 64. What percent of 55 is 88? 65. 45 is 3% of what number? 66. The 3200 people who vote in an election are 40% of the people registered to vote. How many are registered? 67. If you get 36 on a 40-question test, what percent is this? 68. What is the average of 87, 36, 48, 59, and 95? 69. If two test scores are 85 and 60, what minimum score on the next test would be needed for an overall average of 80? 70. The average height of 49 people is 68 inches. What is the new average height if a 78-inch person joins the group? Problems 71-72: s varies directly as P, and P = 56 when s = 14 : 71. Find s when P = 144 . 72. Find P when s = 144 . 2 Problems 73-74: A is proportional to r , and when r = 10 , A = 400π . 73. Find A when r = 15 . 74. Find r when A = 36π 75. If b is inversely proportional to h, and b = 36 when h = 12 , find h when b = 3 . 76. If 3x = 4 y , write the ratio x : y as the ratio of two integers. 18 78. After a rectangular piece of knitted fabric shrinks in length 1 cm and stretches in width 2 cm, it is a square. If the original area was 40 cm 2 , what is the square area? 77. The length of a rectangle is twice the width. If both dimensions are increased by 2 cm, the resulting rectangle has area 84 cm 2 . What was the original width? Answers: 1. 144 2. x + 2, x − 2 3. 46 4. 9 5. 1 2 6. 1 7. 0,1, or 2 8. 0, 1, 2, 3, or 4 9. Inside circle of radius 4 centered on A 10. x − 16 11. y + z 12. 2ab, yes: (a + b)2 = a + 2ab + b 2 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 2 x = 40 7 ; y = 16 3 10 times the original side x 3 2 450 mph 4 4 9 hours 450x miles 400 mph 3000 miles 1 2 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 5 x 2 400 min. 3 4 15 3x 4 5 4 5x 4 100 225 .03x .1y 140 x + y + 10 x + y +10 =140 11.2 .03x + .1 y .03 x + .1 y = 11.2 x = 180 7 ; y = 730 7 6, -6 4.5, -4.5 2 x 2x y 3: 2 or 3 2 45 2M=W 6 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. B 125% 80% C 166 2 3 % 60% 75% 25% decrease lower 96% same (96%) 1.08 62.5% 160% 1500 8000 90% 65 95 68.2 inches 36 576 900π 3 144 4:3 5 cm 49