$\Leftrightarrow x^2+2x-1=(2x+1)(\sqrt{x^2+2x+3}-2)$$\Leftrightarrow (x^2+2x-1)$ $(1-\frac{2x+1}{\sqrt{x^2+2x+3}+2})$ $=0$
$\Rightarrow x^2+2x-1=0\Rightarrow x_1=-1+\sqrt{2};x_2=-1-\sqrt{2}$
hoặc đỏ=0 $\Rightarrow \sqrt{x^2+2x+3}=2x-1$
$\Rightarrow x^2+2x+3=4x^2-4x+1$ $DK:x\geq \frac{1}{2}$
$\Rightarrow 3x^2-6x-2=0$
$\Rightarrow x_3=\frac{3+\sqrt{15}}{3}$ hoặc $x_4=\frac{3-\sqrt{15}}{3}$ ( loại)