Evaluate the summation: sum_{k=1}^{20} (4k - 3).
Answer and explanation
Correct answer: B. 780
- Step 1: This is an arithmetic series with n = 20. Step 2. Find first term: a_1 = 4(1) - 3 = 1. Step 3. Find last term: a_20 = 4(20) - 3 = 77. Step 4. Compute sum: S_20 = 20 (1 + 77) / 2 = 10 78 = 780. Answer: 780. Why not the others: 740 and 760 miss the endpoint values or use 19 terms; 790 is an addition slip.
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