2. 外语
  3. 1,-3,4,1,-3,4,1,-3,4,... In the sequence above, the first 3 terms repeat without end. What is the sum of the terms of the sequen

1,-3,4,1,-3,4,1,-3,4,... In the sequence above, the first 3 terms repeat without end. What is the sum of the terms of the sequen

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问题 1,-3,4,1,-3,4,1,-3,4,...
In the sequence above, the first 3 terms repeat without end. What is the sum of the terms of the sequence from the 150th term to the 154th term?
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答案7
解析 Examining the repeating pattern, you see that the 3rd term is 4, and every 3rd term after that, in other words, the 6th, 9th, 12th, 15th, and so on, is 4. Since 150 is a multiple of 3, the 150th term is 4. Therefore the 150th to the 154th terms are 4, 1, -3, 4,1. The sum of these 5 terms is 7, so the correct answer is 7.
This explanation uses the following strategy.
Strategy 7: Find a Pattern
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