The number of solution $(s)$ of the equation $log_7(2^x -1) + log_7(2^x -7) = 1$, is -
$0$
$1$
$2$
$3$
If ${a^2} + 4{b^2} = 12ab,$ then $\log (a + 2b)$ is
If $x = {\log _5}(1000)$ and $y = {\log _7}(2058)$ then
The set of real values of $x$ for which ${\log _{0.2}}{{x + 2} \over x} \le 1$ is
If $A = {\log _2}{\log _2}{\log _4}256 + 2{\log _{\sqrt 2 \,}}\,2,$ then $A$ is equal to
If $x = {\log _a}(bc),y = {\log _b}(ca),z = {\log _c}(ab),$then which of the following is equal to $1$