$x^{2}$ - 4x +3 $\geq$ 0

<=> $x^{2}$ -3x-x +3 $\geq$ 0

<=> x(x-1 )-3 (x-1)$\geq$ 0

<=> (x-1) (x-3)$\geq$ 0

<=> +) $\left \{ {{x-1 \geq 0} \atop {x-3 \geq}0} \right.$  

         +) $\left \{ {{x-1\leq 0} \atop {x-3\leq 0}} \right.$ 

<=> +) $\left \{ {{x\geq 1} \atop {x\geq 3}} \right.$  

         +) $\left \{ {{x\leq1} \atop {x\leq 3}} \right.$  

<=>  +) x$\geq$ 3

          +) x$\leq$ 1

Vậy...................

`x^2-4x+3≥0`

`x^2-x-3x+3≥0`

`x(x-1)-3(x-1)≥0`

`(x-3)(x-1) ≥ 0 `

\(\left[ \begin{array}{l}\left \{ {{x-3≥0} \atop {x-1≥0}} \right.\\\left \{ {{x-3\leq0} \atop {x-1\leq0}} \right.\end{array} \right.\) 

\(\left[ \begin{array}{l}\left \{ {{x≥3} \atop {x≥1}} \right.\\\left \{ {{x\leq3} \atop {x\leq1}} \right.\end{array} \right.\)

\(\left[ \begin{array}{l}x\geq3\\x\leq1\end{array} \right.\)

Vậy `x≥3` hoặc `x≤1`