The first term of an arithmetic progression is and its common difference is . What is the sum of its first terms?
Answer and explanation
Correct answer: D. 616
**
- Step 1: Apply the arithmetic series sum formula .
- Step 2: Substitute , , and : .
- Step 3: Computing the expression yields .
Answer
616.
Why not the others: '611' evaluates the summation using terms instead of ; '632' omits the factor of in the series formula; '1296' adds rather than subtracts the common difference term.
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