a) \(-5< x< 1\)
\(\Leftrightarrow x\in\left\{-4;-3;-2;-1;0\right\}\)
b) Ta có: \(\left|x\right|< 3\)
Mà \(\left\{{}\begin{matrix}\left|x\right|\ge0\\\left|x\right|< 3\end{matrix}\right.\) nên \(0\le\left|x\right|< 3\)
\(\Rightarrow\left|x\right|\in\left\{0;1;2\right\}\Leftrightarrow x\in\left\{0;\pm1;\pm2\right\}\)
Vậy \(x\in\left\{0;\pm1;\pm2\right\}\)
c) Ta có: \(\left(x-3\right)\left(x-5\right)< 0\)
\(\Leftrightarrow x-3\) và \(x-5\) trái dấu
Dễ thấy \(x-5< x-3\)
Nên \(\left\{{}\begin{matrix}x-5< 0\\x-3>0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x< 5\\x>3\end{matrix}\right.\) \(\Leftrightarrow3< x< 5\)
Vậy \(3< x< 5\)
