\(G=1-\sqrt{x}-\dfrac{\sqrt{x}+x}{\sqrt{x}}\left(x>0\right).\)
\(G=\dfrac{\sqrt{x}-x-\sqrt{x}-x}{\sqrt{x}}=\dfrac{-2x}{\sqrt{x}}=-2\sqrt{x}.\)
\(G+x-8=0.\\ \Rightarrow-2\sqrt{x}+x-8=0.\\ \Leftrightarrow\left(\sqrt{x}-4\right)\left(\sqrt{x}+2\right)=0.\\ \Leftrightarrow\left[{}\begin{matrix}\sqrt{x}=4.\\\sqrt{x}=-2\left(vôlý\right).\end{matrix}\right.\)
\(\Rightarrow x=16.\)