CA Foundation P3 · Chapter 1 · Question 9 of 9
If a² + b² = 7ab (a, b > 0), then log((a + b)/3) is equal to:
Test yourself: pick an answer
Reveal answer & explanation
Correct answer: B) ½(log a + log b)
Explanation
Adding 2ab to both sides gives a² + 2ab + b² = 9ab, i.e. (a + b)² = 9ab. Hence (a + b)/3 = √(ab). Taking logs, log((a + b)/3) = ½ log(ab) = ½(log a + log b).