b)$\sqrt{x^2-2x+5}+\sqrt{x^2-2x+10}<5 (1)$ta co: $\sqrt{x^2-2x+5}=\sqrt{x^2-2x+1+4}=\sqrt{(x-1)^2+4}\geq \sqrt4=2,\forall x\in R$
$\sqrt{x^2-2x+10}=\sqrt{(x-1)^2+9}\geq \sqrt9=3,\forall x\in R$
$\sqrt{x^2-2x+5}+\sqrt{x^2-2x+10}\geq 2+3=5,\forall x\in R$
Vay pt $(1)$ vo nghiem