\ffor 13. The second term of a geometric sequence is 28 and the fifth term is -224. Write a rule for an (4 points). in11. Find the value of x so that (x - 1), (x + 2), and 3x are three consecutive terms of a geometric sequence (5 points).Worksheet 8.5 1. Find the sum of the first 8 terms of the series: 24 + 12 + 6+... geometric r = - a an = arn - 1 47. 8 125 2. Find the sum of 2 + 6 + 18 + ... + 486. sh = 2 13 758 3. Write in summation notation: 2 + 4 + 8 + 16 + 32 + 64 + 128 Son su = hel 4. Write in summation notation: 2 + 6 + 18 + ... + 4374 5. Write in summation notation: 3 - 6 + 12 - 24 + 48 - 96 + 192. exponent: geomet wos anthmatic 6. Find the sum: 10 [ 6( 2 ) n - 1 n= 1 7. Find the sum: 10 5(2) 12 - 1 n = 48. The sum of the terms of a geometric series is 6560. The first three terms of the series are 2 + 6 + 18. How many terms are there? 9. Write the formula for the nth term of the sequence: 24, -12, 6, -3, ... 10. If Sn = 1533, a1 = 3, and r = 2, find n. 11. The first three terms of the sequence 8, x, y, 36 form an arithmetic sequence and the last three terms form a geometric sequence. Find x and y. Answers: 47.8125 or 47 13 728 2(2 ) n - 1 or n = 1 n=1 2(3)n-1 3(-2) n-1 n=1 12. Find x so that (x - 1), (x + 2), and 3x are three consecutive terms of a geometric 6. 6138 sequence. 7 . 5080 8. 8 9. an = 24 (- 1)"-1 10. 9 11. x = 16, y = 24 Or x = 1,y = -6 12. 4 or - _ 13. 59 or 5.994 13. Find the sum of 14. 10 15. 510 12 i-1 12 16. 4(2)1-1 n = 1 17. 4(-2) n- 1 n = 1 18. a7 = 5 19. $28714. Sonia has 55 blocks. She decides to stack up all the blocks so that each row has one less block than the row below. She wants to end up with just one block on top. How many should she put in the bottom row? 15. Find the sum of 15 ) ( An + 2 ) n=1 16. Write in summation notation: 4 + 8 + 16 + 32 + 64 + 128 + 256 17. Write in summation notation: 4 - 8 + 16 - 32 + 64 - 128 + 256 18. Find the 7th term of the sequence: - 1 1 1 20' 10'5 ' .". 19. Eight people share $2016 among them in such a way that each person receives $10 more than the preceding person. What is the amount of the largest share