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Câu hỏi: Giải bất phương trình ${{\log }_{\dfrac{1}{2}}}\left( 3x-1 \right)>0$.
A. $x>\dfrac{1}{2}$.
B. $x<\dfrac{2}{3}$.
C. $x>\dfrac{2}{3}$.
D. $\dfrac{1}{3}<x<\dfrac{2}{3}$.
Ta có : ${{\log }_{\dfrac{1}{2}}}\left( 3x-1 \right)>0={{\log }_{\dfrac{1}{2}}}1\Leftrightarrow 0<3x-1<1\Leftrightarrow \dfrac{1}{3}<x<\dfrac{2}{3}$.
A. $x>\dfrac{1}{2}$.
B. $x<\dfrac{2}{3}$.
C. $x>\dfrac{2}{3}$.
D. $\dfrac{1}{3}<x<\dfrac{2}{3}$.
Ta có : ${{\log }_{\dfrac{1}{2}}}\left( 3x-1 \right)>0={{\log }_{\dfrac{1}{2}}}1\Leftrightarrow 0<3x-1<1\Leftrightarrow \dfrac{1}{3}<x<\dfrac{2}{3}$.
Đáp án D.