`a)\sqrt{9-4\sqrt{5}}-\sqrt{5}`
`=\sqrt{(\sqrt{5}-2)^2}-\sqrt{5}`
`=\sqrt{5}-2-\sqrt{5}`
`=-2`
Mà `-2=-2`
`->VT=VP`(đpcm)
$b)\dfrac{3}{2}\sqrt{6}+2\sqrt{\dfrac{2}{3}}-4\sqrt{\dfrac{3}{2}}$
$=\dfrac{3\sqrt{6}}{2}+\dfrac{2\sqrt{2}}{\sqrt{3}}-\dfrac{4\sqrt{3}}{\sqrt{2}}$
$=\dfrac{3\sqrt{3}}{\sqrt{2}}-\dfrac{4\sqrt{3}}{\sqrt{2}}+\dfrac{2\sqrt{2}}{\sqrt{3}}$
$=\dfrac{3\sqrt{3}-4\sqrt{3}}{\sqrt{2}}+\dfrac{4}{\sqrt{6}}$
$=\dfrac{-3}{\sqrt{6}}+\dfrac{4}{\sqrt{6}}$
$=\dfrac{-3+4}{\sqrt{6}}$
$=\dfrac{1}{\sqrt{6}}$
$=\dfrac{\sqrt{6}}{\sqrt{6}.\sqrt{6}}$
$=\dfrac{\sqrt{6}}{6}$
mà $\dfrac{\sqrt{6}}{6}=\dfrac{\sqrt{6}}{6}$
$⇒VT+VP(đpcm)$
