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JAMB Mathematics 2013 Question 19

Question 19

Progressions

If the sum of the first two terms of a G.P. is 3 and the sum of the second and the third terms is −6, find the sum of the first term and the common ratio.

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

Answer: A (−5)

Explanation

a(1 + r) = 3 and ar(1 + r) = −6, so r = −2. Then a(−1) = 3 and a = −3. a + r = −5.