\(\left(x-2\right)\left(x-6\right)< 0\)
\(TH1:\hept{\begin{cases}x-2>0\\x-6< 0\end{cases}\Leftrightarrow\hept{\begin{cases}x>2\\x< 6\end{cases}}}\)
\(TH2:\hept{\begin{cases}x-2< 0\\x-6>0\end{cases}\Leftrightarrow\hept{\begin{cases}x< 2\\x>6\end{cases}}}\)
vì (x-2)>(x-6)
=>\(\hept{\begin{cases}x-2>0\\x-6< 0\end{cases}}=>\hept{\begin{cases}x>2\\x< 6\end{cases}}\)
VẬy 2<x<6
Để \(\left(x-2\right)\left(x-6\right)< 0\)
=> Ta có 2 trường hợp
\(\left(1\right)\hept{\begin{cases}x-2< 0\\x-6>0\end{cases}\Rightarrow\hept{\begin{cases}x< 2\\x>6\end{cases}\Rightarrow x\in O}}\)
\(\left(2\right)\hept{\begin{cases}x-2>0\\x-6< 0\end{cases}\Rightarrow\hept{\begin{cases}x>2\\x< 6\end{cases}\Rightarrow2< x< 6}}\)
=> x = {3 ; 4 ; 5}