Lời giải:
ĐKXĐ: $x>0$
PT $\Rightarrow x+\sqrt{x(x+1)}=1$
$\Leftrightarrow \sqrt{x(x+1)}=1-x$
\(\Rightarrow \left\{\begin{matrix} 1-x\geq 0\\ x(x+1)=(1-x)^2\end{matrix}\right.\Leftrightarrow \left\{\begin{matrix} x\leq 1\\ 3x=1\end{matrix}\right.\Rightarrow x=\frac{1}{3}\) (thỏa đkxđ)