(UFSM) Efetuando o produto $\phantom{X}\dfrac{\;2\,-\,\sqrt{\,3\;}\;}{\sqrt{\,5\;}}\,\centerdot \,\dfrac{\;\sqrt{\,3\;}\,+\,2\;}{\sqrt{\,5\;}\,-\,1}\phantom{X}$ teremos:
a)
$\,\dfrac{1}{\;5\,+\,\sqrt{\,5\;}\;}\phantom{X}$
b)
$\,\dfrac{\;5\,+\,\sqrt{\,5\;}\;}{20}\,$
c)
$\,\dfrac{1}{\;25\,-\,\sqrt{\,5\;}\;}\,$
d)
$\,\dfrac{\;4\,-\,2\sqrt{\,3\;}}{\;2\sqrt{\,5\;}\,-\,1\;}\,$
