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Mathematics LibreTexts

13.1.12: Chapter 12

( \newcommand{\kernel}{\mathrm{null}\,}\)

Be Prepared

12.1

5, 7, 9, 11

12.2

−1,1,−1,1

12.3

20

12.4

3, 7, 11, 15

12.5

( 5 , 2 ) ( 5 , 2 )

12.6

654

12.7

3 4 3 4

12.8

81; 116116

12.9

12; 36; 108

12.10

35

12.11

9 x 2 + 30 x + 25 9 x 2 + 30 x + 25

12.12

x 2 2 x y + y 2 x 2 2 x y + y 2

Try It

12.1

−1 , 2 , 5 , 8 , 11 −1 , 2 , 5 , 8 , 11

12.2

−3 , −1 , 1 , 3 , 5 −3 , −1 , 1 , 3 , 5

12.3

7 , 13 , 31 , 85 , 247 7 , 13 , 31 , 85 , 247

12.4

−3 , −1 , 3 , 11 , 27 −3 , −1 , 3 , 11 , 27

12.5

−1 , 4 , −9 , 16 , −25 −1 , 4 , −9 , 16 , −25

12.6

1 , −8 , 27 , −64 , 125 1 , −8 , 27 , −64 , 125

12.7

a n = 3 n a n = 3 n

12.8

a n = 5 n a n = 5 n

12.9

a n = ( −1 ) n 3 n a n = ( −1 ) n 3 n

12.10

a n = ( −1 ) n + 1 n 2 a n = ( −1 ) n + 1 n 2

12.11

a n = 1 2 n a n = 1 2 n

12.12

a n = 1 n 2 a n = 1 n 2

12.13

2 , 1 , 1 3 , 1 12 , 1 60 2 , 1 , 1 3 , 1 12 , 1 60

12.14

3 , 3 2 , 1 2 , 1 8 , 1 40 3 , 3 2 , 1 2 , 1 8 , 1 40

12.15

1 2 , 1 6 , 1 12 , 1 20 , 1 30 1 2 , 1 6 , 1 12 , 1 20 , 1 30

12.16

1 2 , 1 3 , 1 4 , 1 5 , 1 6 1 2 , 1 3 , 1 4 , 1 5 , 1 6

12.17

45

12.18

60

12.19

16 3 16 3

12.20

8

12.21

n = 1 5 1 2 n n = 1 5 1 2 n

12.22

n = 1 5 1 n 2 n = 1 5 1 n 2

12.23

n = 1 5 ( −1 ) n + 1 n 2 n = 1 5 ( −1 ) n + 1 n 2

12.24

n = 1 5 ( −1 ) n 2 n n = 1 5 ( −1 ) n 2 n

12.25

The sequence is arithmetic with common difference d=11d=11. The sequence is arithmetic with common difference d=−6d=−6.
The sequence is not arithmetic as all the differences between the consecutive terms are not the same.

12.26

The sequence is not arithmetic as all the differences between the consecutive terms are not the same. The sequence is arithmetic with common difference d=2.d=2.
The sequence is arithmetic with common difference d=−5.d=−5.

12.27

7 , 3 , −1 , −5 , −9 , 7 , 3 , −1 , −5 , −9 ,

12.28

11 , 3 , −5 , −13 , −21 , 11 , 3 , −5 , −13 , −21 ,

12.29

241

12.30

−106 −106

12.31

a11=2.a11=2. The general term is an=−3n+35.an=−3n+35.

12.32

a19=−55.a19=−55. The general term is an=−4n+21.an=−4n+21.

12.33

a1=5,a1=5,d=4.d=4. The general term is an=4n+1.an=4n+1.

12.34

a1=8,a1=8,d=−3.d=−3. The general term is an=−3n+11.an=−3n+11.

12.35

1,890

12.36

1,515

12.37

2,300

12.38

5,250

12.39

2,670

12.40

3,045

12.41

The sequence is geometric with common ratio r=3.r=3. The sequence is geometric with common ratio r=14.r=14. The sequence is not geometric. There is no common ratio.

12.42

The sequence is not geometric. There is no common ratio. The sequence is geometric with common ratio r=2.r=2. The sequence is geometric with common ratio r=12.r=12.

12.43

7 , −21 , 63 , −189 , 567 7 , −21 , 63 , −189 , 567

12.44

6 , −24 , 96 , −384 , 1536 6 , −24 , 96 , −384 , 1536

12.45

1 6,561 1 6,561

12.46

1 16,384 1 16,384

12.47

a9=39,366.a9=39,366. The general term is an=6(3)n1.an=6(3)n1.

12.48

a11=7,168.a11=7,168. The general term is an=7(2)n1.an=7(2)n1.

12.49

3,145,725 3,145,725

12.50

10,460,353,200 10,460,353,200

12.51

393,204 393,204

12.52

10,230 10,230

12.53

96

12.54

256 3 256 3

12.55

4 9 4 9

12.56

8 9 8 9

12.57

$ 10,000 $ 10,000

12.58

$ 3 , 333.33 $ 3 , 333.33

12.59

$ 88,868.36 $ 88,868.36

12.60

$ 698,201.57 $ 698,201.57

12.61

x 5 + 5 x 4 y + 10 x 3 y 2 + 10 x 2 y 3 x 5 + 5 x 4 y + 10 x 3 y 2 + 10 x 2 y 3
+ 5 x y 4 + y 5 + 5 x y 4 + y 5

12.62

p 7 + 7 p 6 q + 21 p 5 q 2 + 35 p 4 q 3 p 7 + 7 p 6 q + 21 p 5 q 2 + 35 p 4 q 3
+ 35 p 3 q 4 + 21 p 2 q 5 + 7 p q 6 + q 7 + 35 p 3 q 4 + 21 p 2 q 5 + 7 p q 6 + q 7

12.63

x 4 + 8 x 3 + 24 x 2 + 32 x + 16 x 4 + 8 x 3 + 24 x 2 + 32 x + 16

12.64

x 6 + 6 x 5 + 15 x 4 + 20 x 3 + 15 x 2 x 6 + 6 x 5 + 15 x 4 + 20 x 3 + 15 x 2
+ 6 x + 1 + 6 x + 1

12.65

16 x 4 96 x 3 + 216 x 2 216 x + 81 16 x 4 96 x 3 + 216 x 2 216 x + 81

12.66

64 x 6 192 x 5 + 240 x 4 160 x 3 64 x 6 192 x 5 + 240 x 4 160 x 3
+ 60 x 2 12 x + 1 + 60 x 2 12 x + 1

12.67

6 1 1 35

12.68

2 1 1 6

12.69

x 5 + 5 x 4 y + 10 x 3 y 2 + 10 x 2 y 3 x 5 + 5 x 4 y + 10 x 3 y 2 + 10 x 2 y 3
+ 5 x y 4 + y 5 + 5 x y 4 + y 5

12.70

m 6 + 6 m 5 n + 15 m 4 n 2 + 20 m 3 n 3 m 6 + 6 m 5 n + 15 m 4 n 2 + 20 m 3 n 3
+ 15 m 2 n 4 + 6 m n 5 + n 6 + 15 m 2 n 4 + 6 m n 5 + n 6

12.71

x 5 15 x 4 + 90 x 3 270 x 2 x 5 15 x 4 + 90 x 3 270 x 2
+ 405 x 243 + 405 x 243

12.72

y 6 6 y 5 + 15 y 4 20 y 3 + 15 y 2 y 6 6 y 5 + 15 y 4 20 y 3 + 15 y 2
6 y + 1 6 y + 1

12.73

243 x 5 810 x 4 y + 1080 x 3 y 2 243 x 5 810 x 4 y + 1080 x 3 y 2
720 x 2 y 3 + 240 x y 4 32 y 5 720 x 2 y 3 + 240 x y 4 32 y 5

12.74

256 x 4 768 x 3 y + 864 x 2 y 2 256 x 4 768 x 3 y + 864 x 2 y 2
432 x y 3 + 81 y 4 432 x y 3 + 81 y 4

12.75

15 x 4 y 2 15 x 4 y 2

12.76

70 a 4 b 4 70 a 4 b 4

12.77

3,584

12.78

280

Section 12.1 Exercises

1.

−5 , −3 , −1 , 1 , 3 −5 , −3 , −1 , 1 , 3

3.

4 , 7 , 10 , 13 , 16 4 , 7 , 10 , 13 , 16

5.

5 , 7 , 11 , 19 , 35 5 , 7 , 11 , 19 , 35

7.

1 , 5 , 21 , 73 , 233 1 , 5 , 21 , 73 , 233

9.

2 , 1 , 8 9 , 1 , 32 25 2 , 1 , 8 9 , 1 , 32 25

11.

1 , 3 2 , 5 4 , 7 8 , 9 16 1 , 3 2 , 5 4 , 7 8 , 9 16

13.

−2 , 4 , −6 , 8 , −10 −2 , 4 , −6 , 8 , −10

15.

1 , −4 , 9 , −16 , 25 1 , −4 , 9 , −16 , 25

17.

1 , 1 4 , 1 9 , 1 16 , 1 25 1 , 1 4 , 1 9 , 1 16 , 1 25

19.

a n = 8 n a n = 8 n

21.

a n = n + 5 a n = n + 5

23.

a n = e n + 2 a n = e n + 2

25.

a n = ( −1 ) n 5 n a n = ( −1 ) n 5 n

27.

a n = ( −1 ) n n 3 a n = ( −1 ) n n 3

29.

a n = ( −1 ) n 2 n a n = ( −1 ) n 2 n

31.

a n = 1 4 n a n = 1 4 n

33.

a n = n n + 1 a n = n n + 1

35.

a n = 5 2 n a n = 5 2 n

37.

4 , 2 , 2 3 , 1 6 , 1 30 4 , 2 , 2 3 , 1 6 , 1 30

39.

3 , 6 , 18 , 72 , 360 3 , 6 , 18 , 72 , 360

41.

2 , 24 , 720 , 40320 , 3628800 2 , 24 , 720 , 40320 , 3628800

43.

1 , 1 2 , 1 3 , 1 4 , 1 5 1 , 1 2 , 1 3 , 1 4 , 1 5

45.

1 , 1 2 , 2 3 , 3 2 , 24 5 1 , 1 2 , 2 3 , 3 2 , 24 5

47.

2 , 3 2 , 8 3 , 15 2 , 144 5 2 , 3 2 , 8 3 , 15 2 , 144 5

49.

1 + 4 + 9 + 16 + 25 = 55 1 + 4 + 9 + 16 + 25 = 55

51.

5 + 7 + 9 + 11 + 13 + 15 = 60 5 + 7 + 9 + 11 + 13 + 15 = 60

53.

2 + 4 + 8 + 16 = 30 2 + 4 + 8 + 16 = 30

55.

4 1 + 4 1 + 4 2 + 4 6 = 32 3 = 10 2 3 4 1 + 4 1 + 4 2 + 4 6 = 32 3 = 10 2 3

57.

2 + 6 + 12 + 20 + 30 = 70 2 + 6 + 12 + 20 + 30 = 70

59.

1 2 + 2 3 + 3 4 + 4 5 + 5 6 = 71 20 1 2 + 2 3 + 3 4 + 4 5 + 5 6 = 71 20

61.

n = 1 5 1 3 n n = 1 5 1 3 n

63.

n = 1 5 1 n 3 n = 1 5 1 n 3

65.

n = 1 5 2 n n = 1 5 2 n

67.

n = 1 5 ( −1 ) n + 1 3 n n = 1 5 ( −1 ) n + 1 3 n

69.

n = 1 10 ( −1 ) n 2 n n = 1 10 ( −1 ) n 2 n

71.

n = 1 7 ( 2 n + 12 ) n = 1 7 ( 2 n + 12 )

73.

Answers will vary.

75.

Answers will vary.

Section 12.2 Exercises

77.

The sequence is arithmetic with common difference d=8.d=8.

79.

The sequence is not arithmetic.

81.

The sequence is arithmetic with common difference d=−3.d=−3.

83.

11 , 18 , 25 , 32 , 39 11 , 18 , 25 , 32 , 39

85.

−7 , −3 , 1 , 5 , 9 −7 , −3 , 1 , 5 , 9

87.

14 , 5 , −4 , −13 , −22 14 , 5 , −4 , −13 , −22

89.

163 163

91.

131 131

93.

−79 −79

95.

a20=−34.a20=−34. The general term is an=−2n+6.an=−2n+6.

97.

a11=59.a11=59. The general term is an=5n+4.an=5n+4.

99.

a8=−13.a8=−13. The general term is an=−5n+27.an=−5n+27.

101.

a1=11,a1=11,d=3.d=3. The general term is an=3n+8.an=3n+8.

103.

a1=21,a1=21,d=−8.d=−8. The general term is an=−8n+29.an=−8n+29.

105.

a1=−15,a1=−15,d=3.d=3. The general term is an=3n18.an=3n18.

107.

1,635

109.

−1 , 065 −1 , 065

111.

360

113.

6,325

115.

–3,575

117.

6,280

119.

4,125

121.

−3,850 −3,850

123.

Answers will vary.

125.

Answers will vary.

Section 12.3 Exercises

127.

The sequence is geometric with common ratio r=4.r=4.

129.

The sequence is geometric with common ratio r=12.r=12.

131.

The sequence is geometric with a common ratio r=−2.r=−2.

133.

The sequence is geometric with common ratio r=12.r=12.

135.

The sequence is arithmetic with common difference d=5.d=5.

137.

The sequence is geometric with common ratio r=12.r=12.

139.

4 , 12 , 36 , 108 , 324 4 , 12 , 36 , 108 , 324

141.

−4 , 8 , −16 , 32 , −64 −4 , 8 , −16 , 32 , −64

143.

27 , 9 , 3 , 1 , 1 3 27 , 9 , 3 , 1 , 1 3

145.

472,392 472,392

147.

3,072

149.

0.0001 0.0001

151.

a9=2,304.a9=2,304. The general term is an=9(2)n1.an=9(2)n1.

153.

a15=219,683.a15=219,683. The general term is an=−486(13)n1.an=−486(13)n1.

155.

a10=0.000000001.a10=0.000000001. The general term is an=(0.1)n1.an=(0.1)n1.

157.

57,395,624 57,395,624

159.

−65,538 −65,538

161.

7,174,453 59,049 121.5 7,174,453 59,049 121.5

163.

65,534 65,534

165.

4088 4088

167.

29,524 6561 4.5 29,524 6561 4.5

169.

3 2 3 2

171.

9 2 9 2

173.

no sum as r1r1

175.

2,048

177.

1 3 1 3

179.

7 9 7 9

181.

5 11 5 11

183.

$6666.67$6666.67 $4000$4000 $15,000$15,000 $7500$7500

185.

$ 295,581.88 $ 295,581.88

187.

$ 14,234.10 $ 14,234.10

189.

Answers will vary.

191.

Answers will vary.

Section 12.4 Exercises

193.

a 8 + 8 a 7 b + 28 a 6 b 2 + 56 a 5 b 3 a 8 + 8 a 7 b + 28 a 6 b 2 + 56 a 5 b 3
+ 70 a 4 b 4 + 56 a 3 b 5 + 28 a 2 b 6 + 70 a 4 b 4 + 56 a 3 b 5 + 28 a 2 b 6
+ 8 a b 7 + b 8 + 8 a b 7 + b 8

195.

p 9 + 9 p 8 q + 36 p 7 q 2 + 84 p 6 q 3 p 9 + 9 p 8 q + 36 p 7 q 2 + 84 p 6 q 3
+ 126 p 5 q 4 + 126 p 4 q 5 + 84 p 3 q 6 + 126 p 5 q 4 + 126 p 4 q 5 + 84 p 3 q 6
+ 36 p 2 q 7 + 9 p q 8 + q 9 + 36 p 2 q 7 + 9 p q 8 + q 9

197.

a 6 6 a 5 b + 15 a 4 b 2 20 a 3 b 3 a 6 6 a 5 b + 15 a 4 b 2 20 a 3 b 3
+ 15 a 2 b 4 6 a b 5 + b 6 + 15 a 2 b 4 6 a b 5 + b 6

199.

x 3 + 15 x 2 + 75 x + 125 x 3 + 15 x 2 + 75 x + 125

201.

y 7 + 7 y 6 + 21 y 5 + 35 y 4 + 35 y 3 y 7 + 7 y 6 + 21 y 5 + 35 y 4 + 35 y 3
+ 21 y 2 + 7 y + 1 + 21 y 2 + 7 y + 1

203.

z 6 12 z 5 + 60 z 4 160 z 3 + 240 z 2 z 6 12 z 5 + 60 z 4 160 z 3 + 240 z 2
192 z + 64 192 z + 64

205.

243 x 5 405 x 4 + 270 x 3 90 x 2 243 x 5 405 x 4 + 270 x 3 90 x 2
+ 15 x 1 + 15 x 1

207.

27 x 3 135 x 2 + 225 x 125 27 x 3 135 x 2 + 225 x 125

209.

27 x 3 + 135 x 2 y + 225 x y 2 + 125 y 3 27 x 3 + 135 x 2 y + 225 x y 2 + 125 y 3

211.

7 1 1 45

213.

4 1 1 55

215.

m 5 + 5 m 4 n + 10 m 3 n 2 + 10 m 2 n 3 m 5 + 5 m 4 n + 10 m 3 n 2 + 10 m 2 n 3
+ 5 m n 4 + n 5 + 5 m n 4 + n 5

217.

s 7 + 7 s 6 t + 21 s 5 t 2 + 35 s 4 t 3 s 7 + 7 s 6 t + 21 s 5 t 2 + 35 s 4 t 3
+ 35 s 3 t 4 + 21 s 2 t 5 + 7 s t 6 + t 7 + 35 s 3 t 4 + 21 s 2 t 5 + 7 s t 6 + t 7

219.

y 4 12 y 3 + 54 y 2 108 y + 81 y 4 12 y 3 + 54 y 2 108 y + 81

221.

q 3 12 q 2 + 48 q 64 q 3 12 q 2 + 48 q 64

223.

625 x 4 1000 x 3 y + 600 x 2 y 2 625 x 4 1000 x 3 y + 600 x 2 y 2
160 x y 3 + 16 y 4 160 x y 3 + 16 y 4

225.

243 x 5 + 1620 x 4 y + 4320 x 3 y 2 243 x 5 + 1620 x 4 y + 4320 x 3 y 2
+ 5760 x 2 y 3 + 3840 x y 4 + 1024 y 5 + 5760 x 2 y 3 + 3840 x y 4 + 1024 y 5

227.

126 a 5 b 4 126 a 5 b 4

229.

462 x 5 y 6 462 x 5 y 6

231.

112

233.

324

235.

30,618

237.

Answers will vary.

239.

Answers will vary.

Review Exercises

241.

7 , 13 , 31 , 85 , 247 7 , 13 , 31 , 85 , 247

243.

3 4 , 5 16 , 7 64 , 9 256 , 11 1024 3 4 , 5 16 , 7 64 , 9 256 , 11 1024

245.

a n = 9 n a n = 9 n

247.

a n = e n 4 a n = e n 4

249.

a n = n n + 2 a n = n n + 2

251.

1 6 , 1 12 , 1 20 , 1 30 , 1 42 1 6 , 1 12 , 1 20 , 1 30 , 1 42

253.

−3 + ( −1 ) + 1 + 3 + 5 −3 + ( −1 ) + 1 + 3 + 5
+ 7 + 9 = 21 + 7 + 9 = 21

255.

4 + 4 + 2 + 2 3 + 1 6 = 65 6 4 + 4 + 2 + 2 3 + 1 6 = 65 6

257.

n = 1 5 ( −1 ) n 1 3 n n = 1 5 ( −1 ) n 1 3 n

259.

n = 1 5 4 n n = 1 5 4 n

261.

The sequence is arithmetic with common difference d=6.d=6.

263.

5 , 8 , 11 , 14 , 17 5 , 8 , 11 , 14 , 17

265.

−13 , −7 , −1 , 5 , 11 −13 , −7 , −1 , 5 , 11

267.

−129 −129

269.

a18=103.a18=103. The general term is an=7n23.an=7n23.

271.

a1=1,a1=1,d=4.d=4. The general term is an=4n3.an=4n3.

273.

−1,095 −1,095

275.

585 585

277.

4,850 4,850

279.

980 980

281.

The sequence is not geometric.

283.

The sequence is geometric with common ratio r=−2.r=−2.

285.

128 , 32 , 8 , 2 , 1 2 128 , 32 , 8 , 2 , 1 2

287.

1,536 1,536

289.

a12=−25,165,824.a12=−25,165,824. The general term is an=6(−4)n1.an=6(−4)n1.

291.

−43,692

293.

3906.25 3906.25

295.

189 8 = 23.625 189 8 = 23.625

297.

343 6 57.167 343 6 57.167

299.

4 11 4 11

301.

$ 1,634,421.27 $ 1,634,421.27

303.

x 4 4 x 3 y + 6 x 2 y 2 4 x y 3 + y 4 x 4 4 x 3 y + 6 x 2 y 2 4 x y 3 + y 4

305.

32 y 5 240 y 4 + 720 y 3 1080 y 2 32 y 5 240 y 4 + 720 y 3 1080 y 2
+ 810 y 243 + 810 y 243

307.

11 1 1 56

309.

1 1 1 55

311.

t 9 9 t 8 + 36 t 7 84 t 6 + 126 t 5 t 9 9 t 8 + 36 t 7 84 t 6 + 126 t 5
126 t 4 + 84 t 3 36 t 2 + 9 t 1 126 t 4 + 84 t 3 36 t 2 + 9 t 1

313.

256 x 4 + 768 x 3 y + 864 x 2 y 2 256 x 4 + 768 x 3 y + 864 x 2 y 2
+ 432 x y 3 + 81 y 4 + 432 x y 3 + 81 y 4

315.

84 a 3 b 6 84 a 3 b 6

317.

135

319.

280

Practice Test

321.

1 4 , 1 5 , 1 6 , 1 7 , 1 8 1 4 , 1 5 , 1 6 , 1 7 , 1 8

323.

−4 + 16 64 + 256 = 204 −4 + 16 64 + 256 = 204

325.

−13 , −10 , −7 , −4 , −1 −13 , −10 , −7 , −4 , −1

327.

a23=59.a23=59. The general term is an=3n10.an=3n10.

329.

1,325 1,325

331.

3,260 3,260

333.

The sequence is geometric with common ratio r=13.r=13.

335.

5,242,880 5,242,880

337.

797,162 797,162

339.

5 6 5 6

341.

$ 1,409,344.19 $ 1,409,344.19

343.

8 1 1 210


13.1.12: Chapter 12 is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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