Sum of the values of x satisfying the equation $\sqrt{2\mathrm{x}+\sqrt{2\mathrm{x}+4}}=4$ is _____.

$\begin{array}{l}\sqrt{2\mathrm{x}+\sqrt{2\mathrm{x}+4}}=4\\ \Rightarrow \sqrt{2\mathrm{x}+4}=16-2\mathrm{x}\\ \Rightarrow 2\mathrm{x}+4=4(8-\mathrm{x}{)}^2\\ \Rightarrow 2{\mathrm{x}}^2-33\mathrm{x}+126=0\\ \Rightarrow (2\mathrm{x}-21)(\mathrm{x}-6)=0\\ \Rightarrow \mathrm{x}=6,21/2\end{array}$

But x = 21/2 does not satisfy the given equation.