`a)x^2-4x=0`
`=>x.x-4.x=0`
`=>x(x-4)=0`
`=>` \(\left[ \begin{array}{l}x=\\x-4=0\end{array} \right.\)
`=>`\(\left[ \begin{array}{l}x=0\\x=4\end{array} \right.\)
Vậy `x=0;x=4`
$\\$
`b)x^2-4x+3=0`
`=>x^2-x-3x+3=0`
`=>x(x-1)-3(x-1)=0`
`=>(x-1)(x-3)=0`
`=>` \(\left[ \begin{array}{l}x-1=0\\x-3=0\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=1\\x=3\end{array} \right.\)
Vậy `x=1;x=3`
