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WAEC Further Mathematics 2018 Question 8

Question 8

Indices and Logarithms

If log3 a + 2 = 3 log3 b, express a in terms of b.

  1. A.a = b3 − 3
  2. B.a = b3 − 9
  3. C.a = 9b3
  4. D.a = b3/9
Show the answer and explanation

Answer: D (a = b3/9)

Explanation

log₃ a − log₃ b³ = −2, so a/b³ = 3⁻² = 1/9 and a = b³/9.