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WAEC Further Mathematics 2022 Question 26

Question 26

Sequences and Series

The first, second and third terms of an exponential sequence (G.P) are (x − 4), (x + 2) and (3x + 1) respectively. Find the values of x.

  1. A.−1/2, 8
  2. B.1/2, −8
  3. C.−1/2, −8
  4. D.1/2, 8
Show the answer and explanation

Answer: A (−1/2, 8)

Explanation

(x + 2)² = (x − 4)(3x + 1) gives x² + 4x + 4 = 3x² − 11x − 4, so 2x² − 15x − 8 = 0, (2x + 1)(x − 8) = 0: x = −½ or 8.