\(A=\dfrac{\sqrt{8-2.\sqrt{8}.\sqrt{6}+6}}{\sqrt{3}-2}=\dfrac{\sqrt{\left(\sqrt{8}-\sqrt{6}\right)^2}}{\sqrt{3}-2}\)
\(=\dfrac{\left|\sqrt{8}-\sqrt{6}\right|}{\sqrt{3}-2}=\dfrac{\sqrt{8}-\sqrt{6}}{\sqrt{3}-2}=\dfrac{-\sqrt{2}\left(\sqrt{3}-2\right)}{\sqrt{3}-2}\)
\(=-\sqrt{2}\)