Exercises 19.1, page 517

1. $- 3$ $- 3$
3. 4, 6, 8, 10, 12
5. 2.5, 1.5, 0.5. $- 0.5, - 1.5$ $- 0.5, - 1.5$
7. 22
9. $- \frac{16}{3}$ $- \frac{16}{3}$
11. 30.9
13. 49b
15. 544
17. $- \frac{85}{2}$ $- \frac{85}{2}$
19. $n = 6, S_{6} = 150$ $n = 6, S_{6} = 150$
21. $d = - \frac{2}{19}, a_{20} = - \frac{1}{3}$ $d = - \frac{2}{19}, a_{20} = - \frac{1}{3}$
23. $a_{1} = 19, a_{30} = 106$ $a_{1} = 19, a_{30} = 106$
25. $n_{} = 62, S_{n} = - 486.7$ $n_{} = 62, S_{n} = - 486.7$
27. $a_{1} = 360, d = 40, S_{10} = 5400$ $a_{1} = 360, d = 40, S_{10} = 5400$
29. Yes, $d = \ln 2; a_{5} = \ln 48$ $d = \ln 2; a_{5} = \ln 48$
31. $a_{n} = 2 n + 1$ $a_{n} = 2 n + 1$
33. $2 b - c, b, c, 2 c - b, 3 c - 2 b$ $2 b - c, b, c, 2 c - b, 3 c - 2 b$
35. 5050
37. $- 8$ $- 8$
39. $1800 °$ $1800 °$
41. ${2700 m}^{2}$ ${2700 m}^{2}$
43. 195 logs
45. 10 rows
47. 13 years, $11,700
49. 304 ft, 1600 ft
51. Marketing company, $3000
53. $S_{n} = \frac{1}{2} n [2 a_{1} + (n - 1) d]$ $S_{n} = \frac{1}{2} n [2 a_{1} + (n - 1) d]$
55. $a_{1} = 1, a_{n} = n; S_{n} = \frac{n}{2} (a_{1} + a_{n}) = \frac{n}{2} (1 + n) = \frac{1}{2} n (n + 1)$ $a_{1} = 1, a_{n} = n; S_{n} = \frac{n}{2} (a_{1} + a_{n}) = \frac{n}{2} (1 + n) = \frac{1}{2} n (n + 1)$

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Table of Contents for Exercises 19.1, page 517