Answer: n/(2n+1).
- A n/(2n+1)
- B n/(2n-1)
- C 1/(2n+1)
- D n/(n+1)
Correct answer: A. n/(2n+1)
Explanation: Partial fractions (telescoping): 1/((2k-1)(2k+1)) = ½[1/(2k-1) − 1/(2k+1)]. Sum = ½[1 − 1/(2n+1)] = ½ · 2n/(2n+1) = 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