passwella.
Menu

JAMB Mathematics 1989 Question 29

Question 29

Progressions

The sum of the first two terms of a geometric progression is x and the sum of the last two terms is y. If there are n terms in all, then the common ratio is

  1. A.x/y
  2. B.y/x
  3. C.(x/y)1/(n−2)
  4. D.(y/x)1/(n−2)
Show the answer and explanation

Answer: D ((y/x)1/(n−2))

Explanation

x = a + ar and y = arn−2 + arn−1 = rn−2(a + ar). So y/x = rn−2 and r = (y/x)1/(n−2).