[tex]\frac{3}{\sqrt{5}-\sqrt{2} } =\frac{3(\sqrt{5}+\sqrt{2})}{(\sqrt{5}-\sqrt{2} )(\sqrt{5}+\sqrt{2} )} =\frac{3(\sqrt{5}+\sqrt{2})}{(\sqrt{5})^2-(\sqrt{2})^2}=\frac{3(\sqrt{5}+\sqrt{2})}{5-2}=\frac{3(\sqrt{5}+\sqrt{2}) }{3} =\sqrt{5}+\sqrt{2}[/tex]