`D=(sqrt{3}.sqrt{5-2sqrt6})/(sqrt3-sqrt2)-1/(2-sqrt3)`
`=(sqrt3*sqrt{3-2sqrt{3}.sqrt2+2})/(sqrt3-sqrt2)-(2+sqrt3)/(4-3)`
`=(sqrt3.sqrt{(sqrt3-sqrt2)^2})/(sqrt3-sqrt2)-2-sqrt3`
`=sqrt3-2-sqrt3=-2`
c) Ta có: \(C=\sqrt{\dfrac{3\sqrt{5}+1}{2\sqrt{5}-3}}\cdot\left(\sqrt{10}-\sqrt{2}\right)\)
\(=\dfrac{\sqrt{\left(3\sqrt{5}+1\right)\left(2\sqrt{5}-3\right)}}{2\sqrt{5}-3}\cdot\left(\sqrt{10}-\sqrt{2}\right)\)
\(=\dfrac{\sqrt{30-9\sqrt{5}+2\sqrt{5}-3}}{2\sqrt{5}-3}\cdot\left(\sqrt{10}-\sqrt{2}\right)\)
\(=\dfrac{\sqrt{27-7\sqrt{5}}}{2\sqrt{5}-3}\cdot\left(\sqrt{10}-\sqrt{2}\right)\)
\(=\dfrac{\sqrt{54-14\sqrt{5}}}{2\sqrt{10}-3\sqrt{2}}\cdot\left(\sqrt{10}-\sqrt{2}\right)\)
\(=\dfrac{\left(7-\sqrt{5}\right)\cdot\sqrt{2}\left(\sqrt{5}-1\right)}{\sqrt{2}\cdot\left(2\sqrt{5}-3\right)}\)
\(=\dfrac{7\sqrt{5}-7-5+\sqrt{5}}{2\sqrt{5}-3}\)
\(=\dfrac{8\sqrt{5}-12}{2\sqrt{5}-3}\)
\(=\dfrac{4\left(2\sqrt{5}-3\right)}{2\sqrt{5}-3}=4\)
