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For the sequence 23, 19.5, 16, 12.5, the terms are decreasing. The difference between successive terms is -3.5. Therefore, the correct option is: Add the common difference of -3.5.
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The sequence 9, 4, -1, -6 shows a consistent difference of -5 between terms:
- 9 to 4: -5
- 4 to -1: -5
- -1 to -6: -5 Therefore, this is an arithmetic sequence. The correct option is: Arithmetic.
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In the geometric sequence 2, 1/2, 1/8, 1/32, the common ratio can be found by dividing any term by the previous term:
- 1/2 ÷ 2 = 1/4
- 1/8 ÷ 1/2 = 1/4
- 1/32 ÷ 1/8 = 1/4 The common ratio is 1/4. Therefore, the correct option is: 1/4.
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The sequence 19, 15, 11, 7, 3 has a common difference of -4. Therefore, to find a_7:
- a_6 = 3 - 4 = -1
- a_7 = -1 - 4 = -5 Thus, a_7 is: a7=−5.
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The sequence 81, 27, 9, 3, 1, ..., is a geometric sequence where each term is being divided by 3. To find a_7:
- a_6 = 1
- a_7 = 1/3 Therefore, a_7 can be expressed as: a7=1/3.
Please note that there seems to be a typo in your last sequence response regarding a_7. It should denote the correct geometric progression rather than giving an incorrect option like 127. Always check the initial terms to deduce the pattern.