Math 170 Diagnostic Test 4 Answers

1 PRECALCULUS READINESS DIAGNOSTIC TEST PRACTICE Directions: Study the samples, 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 teach or someone else who understands the topic. TOPIC 1: ELEMENTARY OPERATIONS with NUMERICAL and ALGEBRAIC FRACTIONS A. Simplifying fractions (by reducing): example: 9•3 example: 27 = 9•4 = 99 • 43 = 1• 43 = 43 36 (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). 3a 3a•1 example: 12ab = 3a•4 = b (common factor: 3a) 3a 3a • 41b = 1• 41b = 1 4b Problems 1-8: Reduce: 13 = 52 26 = 65 3+6 = 3+9 6axy = 15by 1. 2. 3. 4. 5. 6. 7. 8. 14 x+7y = 7y 5a+b = 5a+c x−3 = 3−x 4( x+2)(x−3) ( x−3)(x−2) example: example: example: x−1 x+1 = (x+1)(x−2) , (x−2)(x−1) x −3x+2 = (x−2)(x+1) = (x+1 )(x−2) = 72 10. 3x 7 = 11. x+3 x+2 4 9 9. 7y 2 example: 3(x+2 and 6(ax : x+1) ) 3(x + 2) = 3• (x + 2) 6(x + 1) = 2 • 3• (x + 1) LCM = 2 • 3• (x + 1) • (x + 2), 12. 30−15a 15−15b 13. x−6 6−x = −2 2 3 and 2 9 17. 15. 3 x and 5 18. 16. x 3 and and 8 . 15 −4 x+1 3 x−2 and x 15(x 2 −2) 4 2−x and 7x (y−1) 10(x−1) D. Adding and subtracting fractions: If denominators are the same, combine the numerators: 3x y − xy = 3x−x y = 2x y If denominators are different, find equivalent fractions with common denominators: example: a2 − a4 = 2a − a4 = 2a−a = a4 4 4 example: 3 x−1 + 1 x+2 3(x+2) (x−1) = (x−1)(x+2) + (x−1)(x+2) = (3x+6+x−1 = (x−14 x+5 x−1)(x+2) )(x+2) C. Finding the lowest common denominator: (LCD) by finding the least common multiple (LCM) of all denominators: 5 6 ax (x+2) 14. = (x−1)(x+2) example: 4 (x+1) = 6(x+1)(x+2) , Problems 14-18: Find equivalent fractions with the lowest common denominator: example: = (1+b )(1−b ) 2•2(x+1) 2•3(x+1)(x+2) and 6(ax = 6(x+1)(x+2) x+1) 2 Problems 9-13: Complete: : 4 = 2•2 6a = 2 • 3• a LCM = 2 • 2 • 3• a = 12a, 9a 2 1 so 43 = 12a , and 6a = 12a = 3 is equivalent to how many eighths? 4 3 2•3 = 8 , 43 = 1• 43 = 22 • 43 = 2•4 = 68 4 6 6 6b = 5ab , 5a6 = bb • 5a = 5ab 5a 3x+2 = 4 (x+1) , 3x+2 = 44 • 3x+2 = 12x+8 x+1 x+1 x+1 4 x+4 x−1 x+1 1 6a and 2 = so 3(x+2 ) B. Equivalent fractions (equivalent ratios): example: 3 4 First find LCM of 6 and 15: 6 = 2• 3 15 = 3• 5 LCM = 2 • 3• 5 = 30 , 8 so 56 = 25 , and 15 = 30 Problems 19-26: Find the sum or difference as indicated (reduce if possible): 19. 20. 21. 22. 16 30 26. 1 + 27 = 23. a3 − 2a = 3 x 3x−2 2 − x−3 = 24. x−2 − x+2 = x−3 b−a − a−b = 25. 2x−1 − 2x−1 = b+a b+a x+1 x−2 x x + 1−x = x−1 1 1 2 + − = (x−1)(x−2) (x−2)(x−3) (x−3)(x−1) 4 7 2 • bd ad = • bd bc 7 7•6 42 example: 2 1 = 2 1 = 4−3 = − − • 6 ( ) 3 2 2 3 E. Multiplying fractions: Multiply the top numbers, multiply the bottom numbers, reduce if possible: example: example: 3 2 • = 4 5 3( x+1) • x−2 6 20 = 103 x 2 −4 x 2 −1 2 7a 28. 3 3( x+4 ) • x 5y 2 5y −16 29. 3x+6 x−1 2 = F. Dividing fractions: Make a compound fraction and then multiply the top and bottom (of the larger fraction) by the LCD of both: Answers: 1. 1 4 2. 2 5 3. 3 4 4. 2ax 5b ÷ 2x = = 15. 16. 17. 6. (can’t reduce) 7. −1 18. 4 (x +2) 8. x−2 9. 32 10. 3xy 11. (x −1) (x + 3) = 2x ÷ b3 = 30. 3 a 31. x+7 x 2 −9 1 x−3 5x 2y = 2a − b 33. 3(x +1) 25. 3 , −4 x− 2 x− 2 2x (x−1) ( ) 30 x −2 (x−1) 2 , 5x 4 xy 1 2 = 3 x 2 +2 x x 2 −4 −3(2 x −1) (x +1)(x −2) 26. 0 27. b 42 −12 3(x +1) , = 42 1 a−4 = 3 − 2 a 24. 2 9 3 5x , x x x (x +1) • 2y 2x • 2y 32. 28. ( ) ( ) 21x x 2 −2 (y−1) 29. 30 x 2 −2 (x−1) 3y 2 x −4 (a + b )(5− p ) 30. 19. 6 7 20. −1 21. 2b−2a b +a 22. 0 23. 5 2 a 12. (1+ b) (2 − a ) a b c d 5x 2y 13. 2 14. 69 , 2x +y y 5a + b 5a + c 5. 5x 2y example: (a +b ) (x−y) (5− p ) • 2 • 2 = (x−y ) (5− p ) (a +b ) 3 • ab = 12 27. 3( x+1)(x+2)( x−2) = (x−2)(x+1)(x−1) = a b c d ÷ dc = a b example: 31. x− y 9 ab x +7 x +3 a 2 −4 a 3−2 a 32. 33. 4a − 2b TOPIC 2: OPERATIONS with EXPONENTS and RADICALS A. Definitions of powers and roots: B. Laws of integer exponents: a b • a c = a b+c ab = a b−c ac I. II. Problems 1-20: Find the value: 1. 2 = 11. 2. 3 = 12. −125 = 52 = 3. −4 = 13. (−5) 4. (−4) = 14. x2 = V. 5. 0 = 15. 6. 1 = 16. a3 = 1 = 4 VI. VII. 17. .04 = 3 2 2 2 4 4 64 = 7. 8. 3 64 = 9. 6 64 = 10. − 49 = 18. 19. 20. 3 2 3 () 2 4 3 4 = = 81a 8 = 7• 7 = (a ) = a b c III. (ab) bc c IV. (ab ) c = ac • bc = ac bc a0 = 1 (if a ≠ 0) a−b = a1b Problems 21-30: Find x: 21. 2 3 • 2 4 = 2 x 22. 23 = 24 −4 23. 3 2x = 1 3x 24. 52 52 = 5x ( ) =2 25. 2 3 4 26. 8 = 2 x x = 42 = 5 4y 3 27. a • a = a 3 28. 10 b b5 x 1 = cx c −4 a 3y − 2 = ax a 2y − 3 29. = bx 30. Problems 58-62: Find x: Problems 31-43: Find the value: 31. 7x = −4 32. 3 = 38. 2 • 4 c+3 39. x c−3 = 33. 2 • 2 = 40. 34. 0 = 41. 35. 5 = 42. a x 0 3 4 5 36. (− 3) − 3 = 3 = x +3 x −3 37. x c + 3 • x c − 3 = Given 47. ) 1 2 68. p p 71. number. (Also true if r is a positive odd integer and a < 0 ). II. r ab = r a • r b , or (ab) r = a r • b 1 a b (a b ) 1 , or r = a b 1 1 1 72. 1 3 54 = 52 = 75. x5 = 78. 5 8 example: example: r ( ) = (a ) r 1 1 r 76. 77. s example: 3 = 5 8 1 = 3 12 2 3 = 3−1 = 5 8 • 3 44 3 3 • 3−1 79. 51. x 2 = 1 52. 2x 2 = 50. () = 80. 53. (2 x ) = 1 2 81. Problems 54-57: Write as a fractional power: 54. 55. 5= 23 = Answers: 1. 8 2. 9 3. − 16 a= 1 57. = a 56. 3 82. 83. 4. 16 5. 0 6. 1 2x 2 2x a2 = a3 = 3 5 a = 3 2+ 2= 5 3− 3= 2 = 2 3 = 3 48 = 3+1 = 3+1 48. 3 2 = 2 49. 4 3 = 3 4x6 = • Problems 79-87: Simplify: 1 3 = E. Rationalization of denominators: r 1 74. Problems 48-53: Write as a radical: 1 − 23 73. x 2x + 2 2x 3 + r 1 1 IV. rs a = r s a = s r a , or a rs = a s 1 2 ) 3 69. 70. 2 3 + 27 − 75 = a ≥ 0 , then a r = r a p = (r a ) , which is a real r 2 ( 67. 3 12 = r 3 64. −8a 6 b−12 = 50 = 66. I. If r is a positive integer, p is an integer, and = 3 64 = x 65. − 81 = C. Laws of rational exponents, radicals: Assume all radicals are real numbers: a b 4 2 Problems 65-78: Simplify (assume all radicals are real numbers): x 2 y 3 z −1 x 5 y −6 z −3 III. r 8 32 = 16 • 2 = 4 2 72 = 3 8 • 3 9 = 23 9 3 54 + 4 3 16 = 3 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 3 a 2 bc 2 ab 2 c 3 example: example: example: −2 3x 3 y 62. x = 4 9 64 = x 3 D. Simplification of radicals: = ( ) 46. ( ) 45. x= ( No negative powers No fraction d −4 d4 59. 63. 9x 6 y −2 Problems 44-47: Write two given ways: 44. 61. Problems 63-64: Write with positive exponents: = a 3x−2 a 2x−3 43. 4• 9= x 60. x 8x = 2 x−1 −3 2x = 6 x −4 ( ) 0 3 x −1 58. 2 3 = 1 = 5 3 = 3 a = b 3 2 = 3 84. 85. 86. 87. 7. 8 8. 4 9. 2 10 16 3 4 2 9+ 3 3−1 2+ 3 2 +1 3 1− 3 3+2 3−2 = 1 2 = = = = 10 4 = 3+ 3 2 = 10. −7 11. –5 12. 5 13. 5 14. x if x ≥ 0 ; − x if x < 0 15. a 16. 1 2 17. .2 18. 16 81 19. 3a 2 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 32. 1 81 33. 128 34. 0 35. 1 36. − 54 2c 37. x 38. 2 3 x− 2 6 39. x 2x +1 4 40. 2 41. x 3 64. 65. –9 66. 5 2 67. 6 3 68. 33 2 69. 2 13 70. 0 71. x 2 x x 2 −9 42. a x +1 43. a 44. 18 = d −8 45. 46. 47. d y2 = 9−1 x −6 y 2 9x 6 a3 = 8−1 a 3 b−3 8b 3 y 9z 2 −3 9 2 x =x y z 3 72. 2 x 51. x 3 = x x 52. 2 x 53. 2x 1 54. 5 2 3 55. 2 2 1 56. a 3 −1 57. a 2 58. 36 59. 4 9 60. 4 61. 2 62. 1 2 3x 3 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. 6 3 80. 5 5 81. 3 82. ab b 3 83. 18 3 84. 3 2 2 85. 3 2 − 3 3 +3 86. −2 48. 3 49. 3 16 3 50. 3 1 2 = 4 2 63. b8 4a4 87. −7 − 4 3 3 y TOPIC 3: LINEAR EQUATIONS and INEQUALITIES A. Solving linear equations: 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: 1. 2 x = 9 2. 3 = 65x 3. 3x + 7 = 6 4. x3 = 45 5. 5 − x = 9 6. x = + 1 7. 4x − 6 = x 2x 5 8. x −1 x +1 = 6 7 9. x − 4 = x2 + 1 10. 23xx+1 = 52 11. 6 − 4 x = x 12. 32xx−2 =4 +1 x +3 2 x −1 =2 14. 7x − 5 = 2x + 10 x 15. 13 = x +8 13. B. Solving a pair of linear equations: The solution consists of an ordered pair, an infinite number of ordered pairs, or no solution. Problems 16-23: Solve for the common solution(s) by substitution or linear combinations: 16. x + 2 y = 7 20. 2 x − 3 y = 5 17. x + y = 5 21. 4 x − 1 = y 18. 2 x − y = −9 22. x + y = 3 19. 2 x − y = 1 23. 2 x − y = 3 3 x − y = 28 x − y = −3 x =8 y = x −5 3x + 5 y = 1 4x + y =1 x + y =1 6 x − 9 = 3y C. Analytic geometry of one linear equation: 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. 5 −3 2 example: y = 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 24-28: Find slope and y-intercept, and sketch graph: 24. y = x + 4 25. y = − 12 x − 3 26. 2y = 4x − 8 27. x − y = − 1 28. x = −3y + 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). 1−0 Slope = −4+2 = −21 Using (-2, 0) and (x, y), y−0 Slope = x + 2 = −12 ; cross multiply, get − 2 y = x + 2, or y = − 12 x − 1 D. Analytic geometry of two linear equations: 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 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 36-43: For each pair of equations in problems 16 to 23, tell whether the lines are parallel, perpendicular, intersecting but not perpendicular, or the same line: 36. 37. 38. 39. Problem 16 Problem 17 Problem 18 Problem 19 Through (-3, 1) and (-1, -4) Through (0, -2) and (-3, -5) Through (3, -1) and (5, -1) Through (8, 0), with slope –1 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 Problem 20 Problem 21 Problem 22 Problem 23 E. Linear inequalities: 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 Problems 29-33: Find an equation of line: 29. 30. 31. 32. 33. 40. 41. 42. 43. Problems 44-50: Solve and graph on a number line: 44. 45. 46. 47. x −3> 4 4x < 2 2x + 1≤ 6 3< x −3 48. 4 − 2x < 6 49. 5 − x > x − 3 50. x > 1+ 4 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 : Problems 51-56: Graph on a number plane: Problems 34-35: Graph and write equation for… 34. The line through (-1, 4) and (-1, 2) 35. The horizontal line through (4, -1) 51. y < 3 52. y > x 53. y ≥ 23 x + 2 54. x < y + 1 55. x + y < 3 56. 2 x − y > 1 6 F. Absolute value equations and inequalities: Subtract 3 Multiply by –1, get 5 > x > 1. (Note that this says x > 1 and x < 5). 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 − x = −1 x =1 or Graph: -1 0 1 2 3 4 5 6 example: 2x + 1 ≥ 3. The absolute value is greater than or equal to 3 for any number ≥ 3 or ≤ −3 . So, 3 − x = −2 − x = −5 x =5 2x + 1 ≥ 3 2x ≥ 2 x ≥1 Graph: -1 0 1 2 3 4 5 6 2 x + 1 ≤ −3 2x ≤ −4 x ≤ −2 Graph: Problems 57-61: Solve and graph on number line: 57. x = 3 58. x = −1 59. x − 1 = 3 or 60. 2 − 3 x = 0 61. x + 2 = 1 -4 -3 -2 -1 0 1 2 3 Problems 62-66: Solve and graph on number line: 62. x < 3 63. 3 < x 64. x + 3 < 1 example: 3 − x < 2 The absolute value of an number between –2 and 2 (exclusive) is less than 2. Write this 65. 1 ≤ x + 3 66. 5 − x < 5 inequality and solve: − 2 < 3 − x < 2 . Answers: 1. 9 2 2. 5 2 3. − 1 3 4. 15 4 5. –4 6. 5 3 7. 2 8. 13 9. 10 10. − 5 4 11. 6 5 12. − 6 5 13. 5 3 14. 3 15. 4 16. (9, -1) 17. (1, 4) 18. (8, 25) 19. (-4, -9) 20. ( 2819 , − 1319 ) 21. ( 1 4 , 0) 22. no solution 23. (a, 2a − 3), where a is any number; infinite number of solutions 24. m = 1, b = 4 4 25. m = − 1 2 , b = −3 -3 26. m = 2, b = −4 27. m = 1, b = 1 -4 1 28. m = − 1 3 , b = 2 3 29. 30. 31. 32. 33. 34. y = − 5 2 x − 13 2 y= x−2 y = −1 y = −x + 8 2 3 45. 46. 47. 48. 49. 50. 51. 52. y = 23 x −5 x = −1 -1 53. 35. y = −1 -1 36. 37. 38. 39. 40. 41. 42. 43. 44. intersecting, not ⊥ 54. ⊥ intersecting, not ⊥ intersecting, not ⊥ intersecting, not ⊥ intersecting, not ⊥ parallel same line x>7 0 7 55. x < 12 x ≤ 52 x >6 0 1 0 2 3 0 6 x > −1 x<4 x>5 0 -1 0 4 5 0 7 64. − 4 < x < − 2 60. x = 61. x = −1, − 3 62. − 3 < x < 3 2 3 56. 57. x = ±3 (on number line) 58. no solution 59. x = −2, 4 -4 -2 0 65. x ≥ − 2 or x ≤ − 4 -3 0 3 -4 -2 0 63. x > 3 or x < − 3 -3 0 66. 0 < x < 10 3 0 10 TOPIC 4: POLYNOMIALS and POLYNOMIAL EQUATIONS A. 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. example: 6 x = 3x 2 Rewrite: 6x − 3x = 0 Factor: 3x (2x − 1) = 0 So 3x = 0 or (2 x −1) = 0 . Thus, x = 0 or x = 1 2 . 2 1. x (x − 3) = 0 7. x − x − 6 = 0 2. x − 2x = 0 2 3. 2 x = x 4. 3x ( x + 4) = 0 5. (x + 2)(x − 3) = 0 8. x = 2 − x 2 9. 6 x = x + 2 2 10. x + x = 6 2 11. 9 + x = 6x 2 6. (2x +1) (3x − 2) = 0 12. 1− x = 2 x 2 B. Monomial factors: The distributive property says ab + ac = a(b + c ) example: x − x = x(x − 1) 2 example: 4 x y + 6 xy = 2 xy(2 x + 3) 2 16. x y − y x = 3 2 4 17. 6 x y − 9 x y = 2 2 C. Factoring: (x − a )(x + b ) + (x − a )(x + c ): 2 The distributive property says jm + jn = j( m + n) . Compare this equation with the following: 2 (x +1)(x + 3) + (x +1)(x − 4) ( ) = ( x + 1) (x + 3) + (x − 4) 2 2 = (x + 1)(x + 7x + 5) ) 2 Problems 18-20: Find P which completes the equation: 18. ( x − 2)( x −1) 2 − ( x − 2)( x + 3) = ( x − 2)( P ) 2 D. 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 example: 3x + 2x − 1 = 0, a = 3 , b = 2 , and 2 c = −1 −2± 2 2 − 4 (3)(−1) = −2± 64 +12 = −2±6 16 x= 2• 3 = −26± 4 = −66 = −1 or 26 = 13 2 example: x − x −1 = 0 , a = 1, b = − 1, c = −1 x = 1± 21+ 4 = 1±2 5 So there are two roots: 1+ 5 2 Problems 13-17: Factor: 2 ( and we get (x + 1) x + 6x + 9 + x − 4 (x + 4 )(x − 3) + (x − 4)(x − 3) = ( x − 3)( P ) 2 20. (2x − 1)(x + 1) − (2x − 1) (x + 3) = (2 x − 1)( P ) 2 13. a + ab 3 2 2 14. a − a b + ab = 2 15. − 4xy + 10x 2 19. Problems 1-12: Solve by factoring: 2 Note that j = x + 1, m = (x + 3) , and n = (x − 4) , and 1− 5 2 Problems 21-24: Solve: 21. x − x − 6 = 0 2 22. x + 2x = − 1 2 23. 2x − x − 2 = 0 2 24. x − 3x − 4 = 0 2 E. Quadratic inequalities: 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 . 2 8 example: x + 5x 2 Half of 5 is 5 2 , and (5 2) = 25 4 , which must be added to complete the square: 2 These two numbers (3 and –2) split the real numbers into three sets (visualize the number line): x 2 + 5x + x (x − 3) x < −2 −2< x < 3 negative negative positive x>3 (x + 2) (x − 3) (x + 2) solution? negative positive positive no yes no positive negative positive 25 4 = (x + ) 5 2 2 2 If the coefficient of x is not 1, factor so it is. ( example: 3 x 2 − x = 3 x 2 − 13 x − 1 6 , and (− 1 6) = 1 36 , so ) Half of − 1 3 is 2 Therefore, if (x − 3) (x + 2) < 0 , then − 2 < x < 3 Note that this solution means that x > − 2 and (x − x + )= (x − ) , and 3(x − x + )= 3 x − x + . Thus, 2 1 3 2 x<3 1 2 6 1 36 1 3 2 1 36 3 36 3 36 (or 1 ) 12 must be added to 3x − x to complete the square. 2 Problems 25-29: Solve, and graph on a number line: 25. x − x − 6 > 0 2 26. x + 2 x < 0 2 27. x − 2x < −1 Problems 30-33: Complete the square, and tell what must be added: 28. x > x 2 29. 2 x + x −1 > 0 2 2 30. x − 10x 2 31. x + x 2 F. 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 coefficient of x, and square it–this is c. Thus c =( ) b 2 2 = 2 b 4 = x 2 + bx + Answers: 1. 0, 3 2. 0, 2 3. 0, 1 2 4. 0, –4 5. –2, 3 6. − 1 2 , 2 3 7. 3, –2 8. –2, 1 9. 2 3 , − 1 2 10. –3, 2 11. 3 12. –1, 1 2 13. a (a + b) ( 14. a a 2 − ab + b 2 15. 2x (−2y + 5x ) 16. xy (x − y ) 17. 3 x y (2 y − 3 x ) 18. x 2 − 3 x − 2 3 2 Problems 34-40: Sketch the graph: 34. y = x 2 35. y = − x 2 36. y = x + 1 2 2 = (x + 33. 2 x + 8 x G. Graphing quadratic functions: , and x + bx + c b2 4 32. x 2 − 23 x ) b 2 2 38. y = (x + 1) 2 39. y = (x − 2) −1 40. y = (x + 2)( x − 1) 2 37. y = x − 3 2 19. 20. 21. 22. 23. 24. 25. x 2 + 2 x − 16 −2 x 2 − 4 x + 4 –2, 3 –1 33. 2( x + 2) 2 , add 8 34. 35. 1± 17 4 –1, 4 x < −2 or x > 3 36. 1 -2 0 26. −2 < x < 0 -2 3 - 37. 0 27. no solution, no graph 28. 0 < x < 1 ) 0 38. 1 29. x < −1 or x > 1 2 -1 39. (2,-1) 30. ( x − 5) 2 , add 25 31. 32. (x + 1 2) , add 2 (x − 3 4) , add 2 1 9 4 16 40. -2 1 9 TOPIC 5: FUNCTIONS A. What functions are and how to write them: The area of a square depends on the side length s, and given s, we can find the area A for that value of s. The side and area can be thought of as an ordered pair: (s, A). For example, (5, 25) is an ordered pair. Think of a function as a set of ordered pairs with one restriction: no two different ordered pairs may have the same first element. Thus {(s , A) : A is the area of the square with side length s} is a function consisting of an infinite set of ordered pairs. A function can also be thought of as a rule: for 2 example, A = s is the rule for finding the area of a square, given a side. The area depends on the given side and we say the area is a function of the side. ' A = f (s )' is read ' A is a function of s' , or ' A = f of s' . There are many functions of s , the 2 2 one here is s . We write this f (s) = s and can 2 translate: ‘the function of s is s ’. Sometimes we 2 write A( s ) = s . This says the area is a function 2 of s, and specifically, it is s . In some relations, as x + y = 25 , y is not a function of x, since both (3, 4) and (3, -4) make the relation true. 2 2 Problems 1-7: Tell whether or not each set of ordered pairs is a function: {(0, 5)} 2. {(1, 3)(−1, 3)(0, −1)} {(3,1)(3, −1)(−1, 0)} 4. 5. 6. 7. {( x , y ) : y = x 2 and x is any real number} {( x , y ) : x = y 2 and y is any real number} {( x , y ) : y = −3 and x is any real number} {( x , y ) : x = 4 and y is any real number} 1. 3. Problems 8-11: Is y a function of x? 8. y = 4 x + x 9. y = x 2 2 2 10. (x + y) = 36 2 11. y = x example: g(3) = π • 32 = 9π 12. Given y = f (x ) = 3 x − 2 ; complete these ordered pairs: (3, __), (0, __), ( 1 2 , __), (__, 10), (__, -1), ( x − 1 , ___) Problems 13-17: Given f ( x ) = 13. f (1) = 14. f (−2) = 15. f (0) = x x +1 Find: 16. f (−1) = 17. f (x − 1) = C. Composition of functions: example: If f ( x) = x , and g(x ) = x − 3 , f (g(x )) is read ‘f of g of x’, and means replace 2 every x in f ( x) = x with g(x ) giving 2 f (g(x )) = (g(x )) , which equals ( x − 3)2 = x 2 − 6 x + 9 . 2 example: g( f (1 2)) = g (1 2) = g(1 4 ) = 41 − 3 = −2 43 2 ( ) Problems 18-26: Use f and g as above: 18. g(f (x ))= 23. f (x )− g(x ) = 20. g(g(x ))= ( ) 19. f (g(1))= 21. f (x )+ g(x ) = 22. f (x )• g(x ) = f (x ) 24. g(x ) = 25. g x 2 = 26. (g(x )) = 2 example: If k (x ) = x 2 − 4 x , for what x is k (x ) = 0 ? If k (x ) = 0 , then x 2 − 4 x = 0 and since x 2−4 x = x (x − 4 ) = 0 , x can be either 0 or 4. (These values of x: 0 and 4, are called ‘zeros of the function’, because each makes the function zero.) Problems 27-30: Find x so: 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 the area when 2 s is 3. When we do this, we find A(3) = 3 = 9 . example: g(x ) is given: y = g( x ) = πx example: g(7) = π •7 2 = 49π example: g(a) = πa 2 example: g(x + h) = π (x + h) 2 = πx 2 + 2πxh + πh 2 2 27. k (x ) = −4 28. k (x ) = 5 29. x is a zero of x (x + 1) 30. x is a zero of (2x 2 − x − 3) D. Graphing functions: An easy way to tell whether a relation between two variables is a function or not is by graphing it: if a vertical line can be drawn which has two or more 10 points in common with the graph, the relation is not a function. If no vertical line touches the graph more than once, then it is a function. example: x = y has this graph: Problems 40-44: For this graph, tell whether the statement is true or false: 2 Not a function (the vertical line hits it more than once). Problems 31-39: Tell whether or not each of the following is a function: 31. 36. 32. 37. 33. 38. 34. 39. 35. 40. g(−1) = g(0 ) 41. g(0) = g(3) 42. g(1) > g(−1) 43. g(−2 ) > g(1) 44. g(2) < g(0) < g(4) To graph y = f (x ), determine the degree of f (x ) if it is a polynomial. If it is linear (first degree) the graph is a line, and you merely plot two points (select any x and find the corresponding y) and draw their line. If f (x )is quadratic (second degree), its graph is a 2 parabola, opening upward if the coefficient of x is positive, downward if negative. To plot any graph, it can be helpful to find the following: a) The y-intercept (find f (0) to locate y-axis crossing) b) The x-intercept (find x for which f (x ) = 0 – x-axis crossing) c) What happens to y when x is very large (positive) or very small negative? d) What happens to y when x is very close to a number which makes the bottom of a fraction zero? e) Find x in terms of y, and find what happens to x as y approaches a number which makes the bottom of a fraction zero. (d, e, and sometimes c above will help find vertical and horizontal asymptotes.) example: y = 3 − x 2 analysis: a quadratic 2 function (due to x ) y-intercept: f (0) = 3 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 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 . x-intercepts: y = 3 − x = 0 so x = ± 3 example: y = x−+21 2 a) y-intercepts: f (0) = −2 b) x-intercept: none, since there is no solution to y= −2 x +1 =0 c) Large x: negative y approaches zero; very negative x makes y positive and going to zero. (So y = 0 , the x-axis, is an asymptote line.) d) The bottom of the fraction, x + 1 , is zero if x = −1 . As x moves to –1 from the left, y gets very large positive, and if x approaches – 1 from above, y becomes very negative. (The line x = −1 is an asymptote.) 11 Graph: e) To solve for x, multiply by x + 1 and divide by y to get x + 1 = − 2 y or x = −2y −1 = −2−y y Note that y close to zero results in a very positive or negative x and means y = 0 is an asymptote, which we already found above in part c. Answers: 1. yes 2. no 3. yes 4. yes 5. no 6. yes 7. no 8. yes 9. no (2 intersecting lines) 10. no (2 parallel lines) 11. yes 12. 7, -2, − 1 2 , 4, 1 3 , 3x − 5 13. 1 2 14. 2 15. 0 16. none (undefined) 17. xx−1 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. x2 − 3 4 x−6 2 x + x−3 3 2 x − 3x 2 x − x+3 Problems 45-54: Sketch the graph: 45. f (x ) = − x 50. y = 2 x 46. y = 4 − x 51. f (x ) = 47. y = x 52. y = 48. y = x − 2 53. y = 49. y = x 2 + 3x − 4 54. y = x2 x− 3 2 46. x −3 −2 x 1 x−2 1 x2 3 x−1 4 47. x2 − 6x + 9 2 –1, 5 –1, 0 –1, 3 2 yes no yes no yes yes yes no yes F T T T T 48. 2 49. 50. 51. 52. 53. 54. TOPIC 6: TRIGONOMETRY A. Trig functions in right triangles: The sine ratio for an acute angle of a right triangle is defined to be the length of the opposite leg to the length of the hypotenuse. Thus the sine ratio B for angle B, abbreviated sin B, is b c . c a A b C The reciprocal of the sine ratio is the cosecant (csc), so csc B = c b . The other four trig ratios (all functions) are cosine = cos = adjacent leg hypotenuse hypotenuse 1 secant = sec = cos = adjacent leg opposite leg tangent = tan = adjacent leg adjacent leg cotangent = cot = ctn = opposite leg Problems 1-8: For this right triangle, give the following ratios: x 1. tan x = 10 6 sin x 2. cos x = 3. cos θ = θ 8 4. sin θ • cos θ = 2 2 5. cos x , which means (cos x ) = 2 sinθ 6. 1 − sin x = 8. cos = θ 7. cos x sinθ = Problems 9-12: For the point (-3, 4) on the above circle, give: r= Note that for any given value of a trig function, (in its range), there are infinitely many values of θ . Problems 13-14: Find two positive and two negative values θ for which: 13. sin θ = −1 14. tan θ = tan 45° Problems 15-16: Given sin θ = 3 5 and π < θ < π , then: 2 15. tan θ = Problems 17-18: Get a similar identity by 2 2 2 dividing a + b = c by: 17. b 2 2 18. a D. Similar triangles: B. Circular trig definitions: Given a circle with radius r, centered on (0, 0). Draw the radius connecting a line from the vertex to any point on the circle, making an angle θ with the positive x-axis (θ may be any real number, positive measure is counterclockwise). The coordinates (x, y) of point P together with radius r are used to define the functions: P (x, y ) sinθ = y r , cosθ = x r , y θ tan θ = x , y r and the reciprocal x functions as before. (Note that for 0<θ < π 2 , these definitions agree with the right triangle definitions. Also note that −1 ≤ sin θ ≤ 1, − 1 ≤ cosθ ≤ 1, and tanθ can be any real number.) y= 9. x = 10. tan θ = 11. cos θ = 12. cot θ • sin θ = 12 16. cos θ = C. Pythagorean relations (identities): 2 2 2 a + b = c (or x 2 + y 2 = r 2 ) 2 2 above, can be divided by c (or r ) 2 2 2 to give a c 2 + b c 2 = c c 2 , or sin2 A + cos 2 A = 1, (or sin2 θ + cos 2 θ = 1) , called an identity because it is true for all values of A for which it is defined. If ∆ABC ~ ∆DEF , and if tan A = 3 4 , then tan D = 3 4 also, since EF : DF = BC : AC = 3 4. 19. Find DC, given DB = 5 and sin E = .4 E. Radians and degrees: For angle θ , there is a point P on the circle, and an arc from A counter-clockwise to P. The length θ° θ of the arc is 360° • C = 360 • 2πr , and the ratio of π the length of arc to radius is 180 • θ , where θ is the number of degrees (and the ratio has no units). This is the radian measure associated with point P. So P can be located two ways: by giving the central angle θ in degrees, or in a number of radii to be wrapped around the circle from point A (the radian measure). π Converting: radians = 180 • degrees or degrees = 180 π • radians. 180 example: π3 (radians ) = π3 • 180 π = 3 = 60° π = 73 π (radians) example: 420° = 420 • 180 (which means that it would take a little over 7 radii to wrap around the circle from A to 420°.) Problems 20-23: Find the radian measure for a central angle of: 20. 36° = 21. −45° = 22. 180° = 23. 217° = Problems 24-26: Find the degree measure, which corresponds to radian measure of: 24. 3π 2 = 25. −3 = 26. − 76π = Problems 27-29: Find the following values by sketching the circle, central angle, and a vertical segment from point P to the x-axis. (Radian 13 measure if no units are given.) Use no tables or calculator. 27. cos 56π = 28. tan(−315°) = Thus all points of the a 3a graph. y = sin3x are found by moving each point of y = sin x graph to 1 3 its previous distance from the yaxis, showing the new graph repeats 3 times in the period of y = sin x , so the period of y = sin x , so the period of y = sin3x is 2π 3 . 29. sin(−225°) = Problems 30-33: Sketch to evaluate without table or calculator: 30. sec180° = 31. cot(− 32π ) = 32. sin π = 33. cos 32π = Problems 40-46: Sketch each graph and find its period and amplitude: F. Trigonometric equations: example: Solve, given that 0 ≤ θ < 2π : tan 2 θ − tanθ = 0 . Factoring, we get tanθ (tanθ − 1) = 0 , which means that tan θ = 0 or tan θ = 1. Thus θ = 0 (degrees or radians) plus any multiple of 180° (or π ), which is n •180° (or n • π ), or θ = 45° ( π 4 radians), or 45 + n • 180° (or π 4 + n • π ). Thus, θ can be 0, π 4 , π , or 5π 4 , which all check in the original equation. Problems 34-39: Solve, for 0 ≤ θ ≤ 2π : 34. sinθ = cosθ 2 35. sin θ = 1+ cosθ 36. sin 2 θ = 1 − cos 2 θ 40. y = cos x 44. y = −4 sin 23 x 41. y = cos2 x 42. y = tan x 43. y = tan x3 45. y = sin 2 x 46. y = 1+ cos x H. Identities: example: Find a formula for cos2A, given cos( A + B ) = cos A cos B − sin A sin B . Substitute A for B: cos2 A = cos( A + A) = cos A cos A − sin A sin A = cos2 A − sin2 A 37. sin θ cot θ = 1 2 38. cosθ tan θ = 1 39. sinθ tan θ = sec θ Problems 47-49: Use sin x + cos x = 1 and the above to show: 2 G. Graphs of trig functions: By finding values of sin x when x is a multiple of π 2 , we can get a quick sketch of y = sin x . The sine is periodic (it repeats every 2 π , its period). sin x never exceeds one, so the amplitude of sin x is 1, and we get this graph: 2 47. cos2 A = 2 cos A −1 2 48. cos2 A = 1− 2sin A 49. cos2 x = 12 (1+ cos 2 x ) 2 50. Given cos A = 1 , sec A sin A cos A = tan A, and sin A + cos A = 1, show that tan2 x + 1= sec 2 x . 2 To graph y = sin3x , we note that for a given value of x, say x = a , the value of y is found on the graph of y = sin x three times as far from the y-axis as a. Answers: 1. 4 3 2. 4 3 3. 4 5 4. 12 25 5. 9 25 6. 9 25 7. 1 8. 3 4 9. –3, 4, 5 10. − 4 3 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 51. Given sin2 A = 2sin A cos A , show 8sin 12 x cos 21 x = 4 sin x . − 35 − 35 − 5π 2 , − π 2 , 3π 2 , 7π 2 −315°, − 135°, 45°, 225° − 34 −45 tan 2 A + 1 = sec 2 A 1 + cot 2 A = csc 2 A 2 π 2 5 21. 22. 23. 24. 25. −π 4 π 217 π 180 270° (− 540 π )° 26. −210° 27. − 3 2 28. 1 29. 2 2 14 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 42. –1 0 0 0 π π 5π π 2, 3π 3, 5π 2 π 3π 2, 2, 3 45. 1 π -1 π P = 2π A =1 2π -1 π 1 3π -4 2 1 41. 44. 4 46. 2 1 -1 P=π A =1 -1 2π π 2 2 48. cos 2A = cos A − sin A = (1− sin 2 A) − sin 2 A =1− 2sin 2 A 49. From problem 47, cos 2 x = 2cos 2 x − 1 . Add 1, divide by 2. 2 50. tan 2 A + 1 = sin 2 A + 1 P = 3π A=4 P=π A = 12 = P = 2π A =1 2π cos 2A = cos 2 A − sin 2 A = cos 2 A − (1− cos 2 A) = 2cos 2 A −1 P = 3π no A 3π 4 π 0 ≤ θ < 2π π P=π no A 2π 43. 4, π 47. sin 2 A + cos 2 A cos 2 A cos A 1 cos2 A = = sec 2 A 51. Multiply given by 4, then let 2 A = x TOPIC 7: LOGARITHMIC and EXPONENTIAL FUNCTIONS Problems 5-25: Use the exponent and log rules to find the value of x: A. Logarithms and exponents: Exponential form: 2 = 8 Logarithmic form: log 2 8 = 3 3 5. 4 3 • 4 5 = 4 x 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 1-4: Write the following information in both exponential and logarithmic forms: 1. The power of 3, which gives 9 is 2. 3 2. The power of x, which gives x is 3. 1 3. 10 to the power − 2 is 100 1 2 4. is the power of 169 which gives 13. −2 6. 3 = x 7. 3x 3 ( ) =5 8. 5 2 3 x 9. log 3 3 = x 7 = 30 =8 log 6 x 10. 6 11. log10 x = log10 4 + log10 2 12. log x 25 = 2 13. log2 321 =x 14. log16 x = 3 2 15. 3log a 4 = log a x 16. log x 3 log x 4 = log 4 3 17. log 3 (27 • 3−4 ) = x 18. log(2 x − 6) = log(6 − x ) 19. log 4 64 = x 23. 27 x = (19 ) 3 20. 4 5 = 5 x 24. 4 = 2 log 3 81 81 21. log 27 − log 3 27 = x 25. 3 • 2 x = 4 x 10 exponent rules: (all quantities real) log rules: (base any positive real number except 1) a b • a c = a b+c ab = ab− c ac log ab = log a + log b log ab = log a − log b Problems 26-31: Find the value: 26. 2 = 29. log a = blog a log a a b = b a(log a b ) = b log b loga b = log c a 27. log 4 4 10 = 28. log 6 6 = 30. log 49 7 = 31. log 7 49 = 32. Find log 3 2 , given: log10 3 = .477 log10 2 = .301 (a ) = a b c (ab) c () a c b 0 b bc = acbc = ac bc a = a = r (think of 22. log 4 3 30 = x log 4 30 10 c a = 1 (if a ≠ 0) a− b = a1b p r 3 p p r as = Problems 33-34: Given log 2 1024 = 10 , find: 33. log 2 1024 5 = ( a) r 610 310 34. log 2 1024 = p power ) root Problems 35-46: Solve for x in terms of y and z: (base change rule) 35. 3x = 3y • 3z 36. 9 y = 3z 3x 15 37. x = y 39. 3• 2 = 2 38. 3x = y 40. log x 2 = 3log y x 3 y 2) Solve for y : x = y − 1, so y = x + 1 ( x ≥ 0 is still true) 2 3) Thus g( x ) = x + 1 (with x ≥ 0) is the inverse function, and has g this graph: Note that the f and g graphs l are reflections of each other in the 45°–line, and that the ordered pair (2,5) satisfies g and (5,2) satisfies f. example: Find the x f inverse of y = f ( x ) = 3 and graph both l functions on one graph: y 1) Switch: x = 3 2) Solve: log 3 x = y = g( x ) , the inverse to get the graph l of g( x ) = log 3 x , f reflect the f graph l over the 45°–line: g 2 41. log x = 2log y − log z 42. 3log x = log y 43. log x = log y + log z 44. log x + log 3 y = log z 2 45. log 7 3 = y; log 7 2 = z x = log 3 2 46. y = log a 9; x = log a 3 B. Inverse functions and graphing: If y = f ( x )and y = g( x ) are inverse functions, then an ordered pair (a, b) satisfies y = f (x ) if and only if the ordered pair (b, a) satisfies y = g( x ). In other words, ‘f and g are inverses of each other’ means f (a) = b if and only if g(b) = a To find the inverse of a function y = f ( x ) 1) Interchange x and y 2) Solve this equation for y in terms of x, so y = g( x ) 3) Then if g is a function, f and g are inverses of each other. 2 Problems 47-48: Find the inverse function and sketch the graphs of both: The effect on the graph of y = f ( x ) when x and y are switched, is to reflect the graph over the 45° line (bisecting quadrants I and III). This reflected graph represents y = g( x ). 47. f (x ) = 3x − 2 48. f ( x ) = log 2 (− x ) (note that –x must be positive, which means x must be negative) example: Find the inverse of f (x ) = x − 1 or y = x −1 1) Switch x and y: 49. 50. 51. 52. f x = y −1 l (note y ≥ 1 and x ≥ 0) Answers: 1. 32 = 9, log 3 9 = 2 2. x 3 = x 3 , log x x 3 = 3 3. 10−2 = 1100 , log10 1100 = −2 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 169 2 = 13, log169 13 = 8 1 1 9 1 6 7 8 8 5 –5 64 1 2 Problems 49-56: Sketch the graph: y = x4 y = 4x y = 4 x −1 y = log 4 x 15. 64 16. any real number > 0 and ≠ 1 17. –1 18. 4 19. 3 20. 1 4 21. 1 3 22. 1 3 23. –2 24. 20 4 − log 3 25. loglog (any base; if 2 base = 2 , x = 2 − log 2 3) 26. 1024 y y y y 53. 54. 55. 56. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. = 4 −x = − log 4 x = 4 x −1 = log4 ( x − 1) 10 1 210 =1024 1 2 2 301 477 50 5 y+z z − 2y 1 37. y 3 38. log 3 y 39. y − log 2 3 40. y 2 = y y 3 16 41. y2 z 49. 53. 1 42. 3 y 43. yz 4 44. 3z 2 50. 54. 1 y 45. z 1 y 46. y 2 47. g( x ) = 13 x + 23 55. 51. (1,1) g 48. g( x ) = −2 x -1 52. f 56. f 1 g TOPIC 8: MATHEMATICAL MODELING–WORD PROBLEMS Before being cut, the large square had area Word Problems: (a + b) . 2 1 3 3 of 6 of 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 Problems 10-11: A B C O 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. 2 The two smaller squares have areas 2 a and b . 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 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 22-25: 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? 17 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? 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… Problems 29-32: If they work together, how many pies can they produce in: 49. Which is correct: 2M=W or M=2W 50. Write the ratio MW+W as the ratio of two integers. 29. 1 minute 30. x minutes Problems 51-53: If A is increased by 25%, it equals B. 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: 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? 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? Problems 62-75: Write an equation for each of the following statement about real numbers and tell whether it is true or false: 62. The product of the squares of two numbers is the square of the product of the two numbers. 63. The square of the sum of two numbers is the sum of the squares of the two numbers 64. The square of the square root of a number is the square root of the square of the number. 65. The square root of the sum of the squares of two numbers is the sum of the two numbers. 66. The sum of the absolute vales of two numbers is the absolute value of the sum of the two numbers. 18 67. The product of the absolute values of two numbers is the absolute value of the product of the two numbers. 68. The negative of the absolute value of a number is the absolute value of the negative of the number. 69. The cube root of the square of a number is the cube of the square root of the number. 70. The reciprocal of the negative of a number is the negative of the reciprocal of the number. 71. The reciprocal of the sum of two numbers is the sum of the reciprocals of the two numbers. 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: 2 (a + b) = a 2 + 2ab + b 2 13. x = 40 7 ; y = 16 3 14. 10 times the original side 15. x 16. 3 2 17. 450 mph 18. 4 4 9 hours 19. 450x miles 20. 400 mph 21. 3000 miles 22. 1 2 23. 5 24. x 2 25. 400 min. 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. 51. 52. 53. 54. 3 72. The reciprocal of the product of two numbers is the product of the reciprocals of the two numbers. 73. The reciprocal of the quotient of two numbers is the quotient of the reciprocals of the two numbers. 74. The multiple of x which gives xy is the multiple of y which gives yx. 75. The power of 2, which gives 2 xy is the power of 2, which gives 2 yx . 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 2:3 45 2M = W 2 3 B 125% 80% C 55. 56. 57. 58. 59. 60. 61. 62. 63. 166 2 3 % 60% 75% 25% decrease lower 96% same (96%) a 2 b 2 = ( ab) 2 T ( a + b) 2 = a 2 + b 2 F ( a) = 2 64. a 2 T (if all expressions are real) 65. a 2 + b 2 = a + b F 66. a + b = a + b F 67. a • b = ab T 68. − a = −a F a2 = ( a) 3 69. 3 70. 1 = − 1a T −a 1 = 1a + 1b F a +b 1 = 1a • 1b T ab 1 1 a = a T 1 b b 71. 72. 73. 74. y = x F 75. xy = yx T F