Answer: −n(2n + 1).
- A n(2n + 1)
- B −n(2n + 1)
- C −n(n + 1)
- D n(n + 1)
Correct answer: B. −n(2n + 1)
Explanation: Grouping in pairs: (2k−1)² − (2k)² = −(4k − 1). Summing k = 1 to n gives −(2n² + n) = −n(2n + 1).
Bar heights for AP 2, 5, 8, 11 with the common difference d=3 marked between consecutive terms.
Concept context
Arithmetic progressions, geometric progressions, and sums