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OAU Post-UTME Mathematics 2011 Question 13

Question 13

Logarithms

Evaluate x if log4(x + 3)(x − 3) = 2

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

Answer: B (5 or −5)

Explanation

(x + 3)(x − 3) = 4² = 16, so x² = 25 and x = 5 or −5.