$${\text{If}}\,{\text{log}}\frac{a}{b} + {\text{log}}\frac{b}{a} = {\text{log}}(a + b),$$      then:

A. a + b = 1

B. a - b = 1

C. a = b

D. a² - b² = 1

Answer: Option A

Solution(By Examveda Team)

$$\eqalign{ & \log {a \over b} + \log {b \over a} = \log \left( {a + b} \right) \cr & \Rightarrow \log \left( {a + b} \right) = \log \left( {{a \over b} \times {b \over a}} \right) = \log 1 \cr & So,a + b = 1 \cr} $$