[tex]\tt \cfrac{1}{2\sqrt{3}+1}-\cfrac{1}{2\sqrt{3}-1}=\cfrac{1(2\sqrt{3}-1)-1(2\sqrt{3}+1)}{(2\sqrt{3}+1)(2\sqrt{3}-1)}=\cfrac{2\sqrt{3}-1-2\sqrt{3}-1}{(2\sqrt{3})^2-1^2}=\\\\\\= \cfrac{-2}{12-1}=-\cfrac{2}{11}[/tex]
[tex]\frac{1}{2\sqrt{3}+1 }-\frac{1}{2\sqrt{3}-1 }=\frac{2\sqrt{3}-1-2\sqrt{3}-1}{(2\sqrt{3}+1)(2\sqrt{3}-1)}=\frac{-2}{(2\sqrt{3})^{2}-1^{2}}=-\frac{2}{12-1}=-\frac{2}{11}[/tex]
