Khẳng định nào sau đây là sai ?
-
A.
\({\log _3}x < 0 \Leftrightarrow 0 < x < 1\)
-
B.
\({\log _{\dfrac{1}{3}}}a > {\log _{\dfrac{1}{3}}}b \Leftrightarrow 0 < a < b\)
-
C.
\(\ln x > 0 \Leftrightarrow x > 1\)
-
D.
\({\log _{\dfrac{1}{2}}}a > {\log _{\dfrac{1}{2}}}b \Leftrightarrow a = b > 0\)
\({\log _a}x > 0 \Leftrightarrow \left[ \begin{array}{l}\left\{ \begin{array}{l}0 < a < 1\\0 < x < 1\end{array} \right.\\\left\{ \begin{array}{l}a > 1\\x > 1\end{array} \right.\end{array} \right.\) ;\({\log _a}x > {\log _a}y \Leftrightarrow \left[ \begin{array}{l}\left\{ \begin{array}{l}a > 1\\x > y\end{array} \right.\\\left\{ \begin{array}{l}0 < a < 1\\x < y\end{array} \right.\end{array} \right.\)
A: \({\log _3}x < 0 \Leftrightarrow 0 < x < 1 \Rightarrow \) A đúng
B: \({\log _{\dfrac{1}{3}}}a > {\log _{\dfrac{1}{3}}}b \Leftrightarrow 0 < a < b \Rightarrow \)B đúng
C: $\ln x > 0 $ ⟺ $x >1 $ ⇒ C đúng
D: \({\log _{\dfrac{1}{2}}}a > {\log _{\dfrac{1}{2}}}b \Leftrightarrow b > a > 0\)⇒ D sai
Đáp án : D
Danh sách bình luận