(x-1).(x-3)=0
⇒x-1=0 hoặc x-3=0
x=1 hoặc x=3
\(\left(x-1\right).\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x-3=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1\\x=3\end{matrix}\right.\)
\(\Rightarrow x\in\left\{1;3\right\}\)
(x-1).(x-3)=0 x-1 là x(1) x-3 là x(2)
=>x-1=0 =>x=0+1=1
=>x-3=0 =>x=0+3=3
vậy x=1(1) x(2)=3
th1: x=1
=> (x-1).(x-3)=0
= (1-1).(1-3)=0 => 0.-2=0
th2: x=3
=>(x-1).(x-3)=0
= (3-1).(3-3)=0 => 0.2 = 0
vậy x ∈ {1;3}