\(a,=6\sqrt{2}-14\sqrt{2}-6\sqrt{2}+15\sqrt{2}=\sqrt{2}\\ b,=\sqrt{\left(2+\sqrt{5}\right)^2}+\left|2-\sqrt{5}\right|=2+\sqrt{5}+\sqrt{5}-2=2\sqrt{5}\\ c,=\dfrac{x+\sqrt{x}-x+\sqrt{x}}{2\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}\cdot\dfrac{\left(\sqrt{x}+1\right)^2}{\sqrt{x}}=\dfrac{2\sqrt{x}}{2\sqrt{x}\left(\sqrt{x}-1\right)}=\dfrac{1}{\sqrt{x}-1}\)
\(a.=6\sqrt{2}-14\sqrt{2}-6\sqrt{2}+15\sqrt{2}=\sqrt{2}\)
\(b.\left|2+\sqrt{5}\right|+\left|2-\sqrt{5}\right|=2+\sqrt{5}+2-\sqrt{5}=4\)
\(c.=\left(\dfrac{\sqrt{x}}{2\left(\sqrt{x}-1\right)}-\dfrac{\sqrt{x}}{2\left(\sqrt{x}+1\right)}\right):\dfrac{\sqrt{x}}{x+2\sqrt{x}+1}\)
\(=\dfrac{x+\sqrt{x}-x+\sqrt{x}}{2\left(x-1\right)}\cdot\dfrac{x+2\sqrt{x}+1}{\sqrt{x}}\)
\(=\dfrac{\sqrt{x}}{x-1}\cdot\dfrac{x+2\sqrt{x}+1}{\sqrt{x}}=\dfrac{x+2\sqrt{x}+1}{x-1}\)
