If $0 < a < 1$,$0 < x < 1$,and $x < a$,then $\log_{a} x$ is:

If $a^{2}+b^{2}=c^{2},$ then $\frac{1}{\log _{c+a} b}+\frac{1}{\log _{c-a} b}=$

If $\frac{\log x}{b-c} = \frac{\log y}{c-a} = \frac{\log z}{a-b}$,then $xyz = x^a \cdot y^b \cdot z^c = x^{b+c} \cdot y^{c+a} \cdot z^{a+b} = $

The value of $\log _{2} 16$ is

If $\frac{\log x}{2} = \frac{\log y}{3} = \frac{\log z}{5}$,then $yz$ in terms of $x$ is

If $a^{x} = b^{y}$,then