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JAMB Mathematics 1997 Question 19

Question 19

Progressions

Sn is the sum of the first n terms of a series given by Sn = n2 − 1. Find the nth term.

  1. A.4n + 1
  2. B.4n − 1
  3. C.2n + 1
  4. D.2n − 1
Show the answer and explanation

Answer: D (2n − 1)

Explanation

Tn = Sn − Sn−1 = (n² − 1) − ((n − 1)² − 1) = 2n − 1.