x 2 – 4 ( x – 2)( x + 2) 0
23. = = x+2, x ≠ 2 30. If = a , then 0 = 0 ⋅ a , but this is meaningless
x–2 x–2 0
because a could be any real number. No
x 2 − x − 6 ( x − 3)( x + 2) 0
24. = = x+2, x ≠3 single value satisfies = a .
x−3 ( x − 3) 0
t 2 – 4t – 21 (t + 3)(t – 7) 31. .083
25. = = t – 7 , t ≠ −3 12 1.000
t +3 t +3
96
2
2x − 2x 2 x(1 − x) 40
26. =
3 2 2
x − 2x + x x( x − 2 x + 1) 36
−2 x( x − 1) 4
=
x( x − 1)( x − 1)
2
=−
x −1
2 Section 0.1 Instructor’s Resource Manual
, 32. .285714 35. 3.6
7 2.000000 3 11.0
14 9
60 20
56 18
40 2
35
36. .846153
50
13 11.000000
49
10 4
10
60
7
52
30
80
28
78
2
20
33. .142857 13
21 3.000000 70
21 65
90 50
84 39
60 11
42
37. x = 0.123123123...
180 1000 x = 123.123123...
168 x = 0.123123...
120 999 x = 123
105 123 41
150 x= =
999 333
147
3 38. x = 0.217171717 …
1000 x = 217.171717...
34. .294117... 10 x = 2.171717...
17 5.000000... → 0.2941176470588235 990 x = 215
34 215 43
x= =
160 990 198
153
39. x = 2.56565656...
70 100 x = 256.565656...
68 x = 2.565656...
20 99 x = 254
17 254
30 x=
99
17
130 40. x = 3.929292…
119 100 x = 392.929292...
11 x = 3.929292...
99 x = 389
389
x=
99
42. x = 0.399999… 55. 8.9π2 + 1 – 3π ≈ 0.000691744752
100 x = 39.99999...
10 x = 3.99999... 56. 4 (6π 2 − 2)π ≈ 3.661591807
90 x = 36
36 2 57. Let a and b be real numbers with a < b . Let n
x= = be a natural number that satisfies
90 5
1 / n < b − a . Let S = {k : k n > b} . Since
43. Those rational numbers that can be expressed a nonempty set of integers that is bounded
by a terminating decimal followed by zeros. below contains a least element, there is a
k 0 ∈ S such that k 0 / n > b but
p ⎛1⎞ 1
44. = p ⎜ ⎟ , so we only need to look at . If (k 0 − 1) / n ≤ b . Then
q ⎝q⎠ q
k0 − 1 k0 1 1
q = 2n ⋅ 5m , then = − >b− > a
n m n n n n
1 ⎛1⎞ ⎛1⎞ k 0 −1 k 0 −1
= ⎜ ⎟ ⋅ ⎜ ⎟ = (0.5)n (0.2)m . The product Thus, a < n ≤ b . If n < b , then choose
q ⎝ 2⎠ ⎝5⎠
k 0 −1 k0 − 2
of any number of terminating decimals is also a r= n . Otherwise, choose r = n .
n m
terminating decimal, so (0.5) and (0.2) , 1
Note that a < b − <r.
1 n
and hence their product, , is a terminating
q Given a < b , choose r so that a < r1 < b . Then
p choose r2 , r3 so that a < r2 < r1 < r3 < b , and so
decimal. Thus has a terminating decimal
q on.
expansion.
58. Answers will vary. Possible answer: ≈ 120 in 3
45. Answers will vary. Possible answer: 0.000001,
1 ft
≈ 0.0000010819... 59. r = 4000 mi × 5280 = 21,120, 000 ft
π 12 mi
equator = 2π r = 2π (21,120, 000)
46. Smallest positive integer: 1; There is no ≈ 132, 700,874 ft
smallest positive rational or irrational number.
60. Answers will vary. Possible answer:
47. Answers will vary. Possible answer: beats min hr day
3.14159101001... 70 × 60 × 24 × 365 × 20 yr
min hr day year
48. There is no real number between 0.9999… = 735,840, 000 beats
(repeating 9's) and 1. 0.9999… and 1 represent 2
⎛ 16 ⎞
the same real number. 61. V = πr 2 h = π ⎜ ⋅12 ⎟ (270 ⋅12)
⎝ 2 ⎠
49. Irrational ≈ 93,807, 453.98 in.3
volume of one board foot (in inches):
50. Answers will vary. Possible answers: 1× 12 × 12 = 144 in.3
−π and π , − 2 and 2 number of board feet:
93,807, 453.98
≈ 651, 441 board ft
51. ( 3 + 1)3 ≈ 20.39230485 144
4 Section 0.1 Instructor’s Resource Manual
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