Cho a, b là hai số số thực dương và \[a \ne 1\]. Khẳng định nào sau đây đúng?

A. −3

B. \[\frac{1}{3}\]

C. \[ - \frac{1}{3}\]

D. 3

A. \[\frac{1}{5}\]

B. \[ - \frac{1}{5}\]

C. 5

D. −5

A. \[{\rm{lo}}{{\rm{g}}_{\rm{a}}}{\rm{c = lo}}{{\rm{g}}_{\rm{a}}}{\rm{b}}{\rm{.lo}}{{\rm{g}}_{\rm{b}}}{\rm{c}}\]

B. \[{\rm{lo}}{{\rm{g}}_{\rm{a}}}{\rm{c = }}\frac{{\rm{1}}}{{{\rm{lo}}{{\rm{g}}_{\rm{c}}}{\rm{a}}}}\]

C. \[{\rm{lo}}{{\rm{g}}_{\rm{a}}}{\rm{b}}{\rm{.lo}}{{\rm{g}}_{\rm{b}}}{\rm{a = 1}}\]

D. \[{\rm{lo}}{{\rm{g}}_{\rm{a}}}{\rm{c = }}\frac{{{\rm{lo}}{{\rm{g}}_{\rm{b}}}{\rm{c}}}}{{{\rm{lo}}{{\rm{g}}_{\rm{b}}}{\rm{a}}}}\]

A. \[{\rm{T}} = - \frac{2}{5}\]

B. \[{\rm{T}} = \frac{2}{5}\]

C. \[{\rm{T}} = \frac{2}{3}\]

D. \[{\rm{T}} = - \frac{2}{3}\]

A. Nếu \[0 < {{\rm{x}}_1} < {{\rm{x}}_2}\]thì \[{\log _a}{{\rm{x}}_1} < {\log _a}{{\rm{x}}_2}\].

B. Nếu \[{\log _a}{\rm{x}} < 1\] thì 0 < x < a

C. Nếu \[{\rm{lo}}{{\rm{g}}_{\rm{a}}}{\rm{x}} > 0\] khi x > 1

D. Nếu \[{\rm{lo}}{{\rm{g}}_{\rm{a}}}{\rm{x > lo}}{{\rm{g}}_{\rm{a}}}{{\rm{x}}^{\rm{2}}}\] thì x > 1

A. \[{\rm{lo}}{{\rm{g}}_{\rm{a}}}{{\rm{a}}^{\rm{b}}}{\rm{ = }}{{\rm{a}}^{\rm{b}}}\]

B. \[{\rm{lo}}{{\rm{g}}_{\rm{a}}}{{\rm{a}}^{\rm{b}}}{\rm{ = a}}\]

C. \[{{\rm{a}}^{{\rm{lo}}{{\rm{g}}_{\rm{a}}}{\rm{b}}}}{\rm{ = }}{{\rm{a}}^{\rm{b}}}\]

D. \[{{\rm{a}}^{{\rm{lo}}{{\rm{g}}_{\rm{a}}}{\rm{b}}}}{\rm{ = lo}}{{\rm{g}}_{\rm{a}}}{{\rm{a}}^{\rm{b}}}\]