Discrete Mathematics and Its Applications, Seventh Edition

Published by McGraw-Hill Education
ISBN 10: 0073383090
ISBN 13: 978-0-07338-309-5

Chapter 2 - Section 2.4 - Sequences and Summations - Exercises - Page 167: 5

Answer

a) 2, 5, 8, 11, 14, 17, 20, 23, 26, 29 b) 1, 1, 1, 2, 2, 2, 3, 3, 3, 4 c) 1, 1, 3, 3, 5, 5, 7, 7, 9, 9 d) -1 ,-2, -2, 8, 88, 656, 4912, 40064, 362368, 3627776 e) 3 ,6, 12, 24, 48, 96, 192, 384, 768, 1536 f) 2, 4, 6, 10, 16, 26, 42, 68, 110, 178 g) 1, 2, 2, 3, 3, 3, 3, 4, 4, 4 h) 3, 3, 5, 4, 4, 3, 5, 5, 4, 3

Work Step by Step

A. Sequence starts with 2, thus a1 = 2. Each next term is the previous term that will be increased by 3. a2 = a1 + 3 = 2 + 3 = 5 a3 = a2 + 3 = 5 + 3 = 8 a4 = a3 + 3 = 8 + 3 = 11 a5 = a4 + 3 = 11 + 3 = 14 a6 = a5 + 3 = 14 + 3 = 17 aA7 = a6 + 3 = 17 + 3 = 20 a8 = a7 + 3 = 20 + 3 = 23 a9 = a8 + 3 = 23 + 3 = 26 a10 = a9 + 3 = 26 + 3 = 29 B. Sequence involves positive numbers in increasing numbers starting from 1 as the first term. Each term happens 3 times. a1 = 1 a2 = 1 a3 = 1 a4 = 2 a5 = 2 a6 = 2 a7 = 3 a8 = 3 a9 = 3 a10 = 4 C. Sequence involves odd positive numbers in increasing numbers starting from 1 as the first term. Each term happens twice. a1 = 1 a2 = 1 a3 = 3 a4 = 3 a5 = 5 a6 = 5 a7 = 7 a8 = 7 a9 = 9 a10 = 9 D. Using the given an=n!−2^n , substitute and evaluate An at n=1,2,3,4,5,6,7,8,9,10. a1 = 1! -2^1 a1 = 1 - 2 = -1 a2 = 2! -2^2 a2 = 2 - 4 = -2 a3 = 3! -2^3 a3 = 6 - 8 = -2 a4 = 4! -2^4 a4 = 24 - 16 = 8 a5 = 5! -2^5 a5 = 120 - 32 = 88 a6 = 6! -2^6 a6 = 720 - 64 = 656 a7 = 7! -2^7 a7 = 5040 - 128 = 4912 a8 = 8! -2^8 a8 = 40320 - 256 = 40064 a9 = 9! -2^9 a9 = 362880 - 512 = 362368 a10 = 10! -2^10 a10 = 3628800 - 1024 = 3627776 E. Sequence begins with the first term = 3. a1 = 3 Each term is twice the previous term. a2 = 2a1 = 2(3) = 6 a3 = 2a2 = 2(6) = 12 a4 = 2a3 = 2(12) = 24 a5 = 2a4 = 2(24) = 48 a6 = 2a5 = 2(48) = 96 a7 = 2a6 = 2(96) = 192 a8 = 2a7 = 2(192) = 384 a9 = 2a8 = 2(384) = 758 a10 = 2a9 = 2(768) = 1536 F. First term = 2. Second term = 4. Every next term is the sum of the two previous term. a3 = 2 + 4 = 6 a4 = 4 + 6 = 10 a5 = 6 + 10 = 16 a6 = 10 + 16 = 26 a7 = 16 + 26 = 42 a7 = 26 + 42 = 68 a9 = 42 + 68 = 110 a10 = 68 + 110 = 178 G. The “n” term is the number of bits in the binary expansions of the number(n). Binary expansion of 1 = 1 a1 = 1 Binary expansion of 2 = 10 a2 = 2 Binary expansion of 3 = 11 a3 = 2 Binary expansion of 4 = 100 a4 = 3 Binary expansion of 5 = 101 a5 = 3 Binary expansion of 6 = 110 a6 = 3 Binary expansion of 7 = 111 a7 = 3 Binary expansion of 8 = 1000 a8 = 4 Binary expansion of 9 = 1001 a9 = 4 Binary expansion of 10 = 1010 a10 = 4 H. The “n” term is the number of letters in the word n. a1 = 3 (one) a2 = 3 (two) a3 = 5 (three) a4 = 4 (four) a5 = 4 (five) a6 = 3 (six) a7 = 5 (seven) a8 = 5 (eight) a9 = 4 (nine) a10 = 3 (ten)
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