\(\left|x\left(x-4\right)\right|=x\\ \Leftrightarrow\left[{}\begin{matrix}x\left(x-4\right)=x\\x\left(x-4\right)=-x\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x^2-4x-x=0\\x^2-4x+x=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x^2-5x=0\\x^2-3x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x\left(x-5\right)=0\\x\left(x-3\right)=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=0\\x=5\end{matrix}\right.\\\left\{{}\begin{matrix}x=0\\x=3\end{matrix}\right.\end{matrix}\right.\)
Vậy có 3 giá trị của x là: \(x=0;\\ x=5;\\ x=3\)
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