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JAMB Mathematics 1998 Question 19

Question 19

Progressions

If p + 1, 2p − 10, 1 − 4p2 are three consecutive terms of an arithmetic progression, find the possible values of p.

  1. A.−4, 2
  2. B.−3, 4/11
  3. C.−11/4, 2
  4. D.5, −3
Show the answer and explanation

Answer: C (−11/4, 2)

Explanation

For an AP, 2(2p − 10) = (p + 1) + (1 − 4p²). This gives 4p² + 3p − 22 = 0, i.e. (4p + 11)(p − 2) = 0, so p = 2 or −11/4.