The third term of an arithmetic sequence is 11 and the seventh term is 23. What is the first term?
Answer and explanation
Correct answer: D. 5
- Step 1: The terms are four common differences apart, so 4d = 23 - 11 = 12 and d = 3. Step 2. The first term is 11 - 2(3) = 5. Answer: 5. Why not the others: 8 is the second term, 3 is the common difference, and 2 subtracts three common differences from the third term instead of two.
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