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JAMB Mathematics 1992 Question 19

Question 19

Progressions

What is the n-th term of the sequence 2, 6, 12, 20, .......?

  1. A.4n − 2
  2. B.2(3n−1)
  3. C.n2 + n
  4. D.n2 + 3n + 2
Show the answer and explanation

Answer: C (n2 + n)

Explanation

2 = 1 × 2, 6 = 2 × 3, 12 = 3 × 4, 20 = 4 × 5, so the nth term is n(n + 1) = n2 + n.