Question

Sum of all the roots of the equation ${\log }_7\left(2^x-1\right)+{\log }_7\left(2^x-7\right)=1$, is

• A. 8
• B. 3
• C. 4
• D. 1

Answer 1

Answer: (B)

$\left(2^x-1\right)\left(2^x-7\right)=7\Rightarrow x=3$ is the only solution.