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WAEC Further Mathematics 2023 Question 2

Question 2

Indices and Logarithms

If (1/9)2x−1 = (1/81)2−3x, find the value of x.

  1. A.3/4
  2. B.5/8
  3. C.−5/8
  4. D.−3/4
Show the answer and explanation

Answer: B (5/8)

Explanation

Write both sides as powers of 3: 3^(−4x + 2) = 3^(−8 + 12x). So −4x + 2 = 12x − 8, 16x = 10 and x = 5/8.