[tex]\displaystyle\bf\\\frac{\sqrt{7}- \sqrt{3} }{\sqrt{7}+\sqrt{3} } +\frac{\sqrt{7} +\sqrt{3} }{\sqrt{7}-\sqrt{3} } =\\\\\\=\frac{(\sqrt{7}-\sqrt{3} )\cdot(\sqrt{7}-\sqrt{3})+(\sqrt{7}+ \sqrt{3})\cdot(\sqrt{7}+ \sqrt{3}) }{(\sqrt{7}+ \sqrt{3})\cdot(\sqrt{7}- \sqrt{3} ) } =\\\\\\=\frac{7-2\sqrt{21} +3+7+2\sqrt{21} +3}{7-3} =\frac{20}{4} =5[/tex]