1)Ta co:$|x^2-7x+5|\geq 0; |2x-5|\geq 0, \forall x\in R$
Do do :$|x^2-7x+5|+|2x-5|=0\Leftrightarrow \left\{ \begin{array}{l} x^2-7x+5=0\\ 2x-5=0 \end{array} \right.$
$\Leftrightarrow\left\{ \begin{array}{l} x=5/2\\ x=\frac{7+\sqrt{29}}{2} hoac x=\frac{7-\sqrt{29}}{2} \end{array} \right.$$\Leftrightarrow x\in \varnothing $
Vay pt da cho vo nghiem