a) Để phân thức \(\dfrac{2}{5-2x}\) không âm thì \(5-2x>0\)
\(\Leftrightarrow2x< 5\)
hay \(x< \dfrac{5}{2}\)
b) Ta có: \(\dfrac{2}{x-1}>1\)
\(\Leftrightarrow\dfrac{2}{x-1}-1>0\)
\(\Leftrightarrow\dfrac{2-x+1}{x-1}>0\)
\(\Leftrightarrow\dfrac{x-3}{x-1}< 0\)
\(\Leftrightarrow\left\{{}\begin{matrix}x-1>0\\x-3< 0\end{matrix}\right.\Leftrightarrow1< x< 3\)
c) Để A dương thì \(\dfrac{x-5}{x-8}>0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-5< 0\\x-8>0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x< 5\\x>8\end{matrix}\right.\)
d) Ta có: \(2-5x< 3\left(2-x\right)\)
\(\Leftrightarrow2-5x< 6-3x\)
\(\Leftrightarrow-5x+3x< 6-2\)
\(\Leftrightarrow-2x< 4\)
hay x>-2
e) ta có: -3x<-7x+5
\(\Leftrightarrow4x< 5\)
hay \(x< \dfrac{5}{4}\)
