$(x^2 + 2)^2 + 4(x+1)^3 + \sqrt{x^2 + 2x +5} = (2x-1)^2 +2$
$\Leftrightarrow (x^2 + 2)^2 - (2x-1)^2 + 4(x+1)^3 + \sqrt{x^2 + 2x +5}=2$
$\Leftrightarrow (x^2 -2x+3(x^2+2x+1) + 4(x+1)^3 + \sqrt{(x+1)^2+4}=2$
$\Leftrightarrow (x+1)^2 [(x+1)^2-4(x+1)]+ 4(x+1)^3 + \sqrt{(x+1)^2+4}=2$
$\Leftrightarrow t^2(t^2-4t) +4t^3 +\sqrt{t^2 +4}=2$
$\Leftrightarrow \sqrt{t^2+4} = 2-t^4$ dễ dàng có $t=0 \Rightarrow x= -1$