[tex]( \sqrt{5} - \sqrt{7} - \sqrt{2})( \sqrt{5} + \sqrt{7} - \sqrt{2}) = \\ \\ \sqrt{5}( \sqrt{5} + \sqrt{7} - \sqrt{2}) - \sqrt{7}( \sqrt{5} + \sqrt{7} - \sqrt{2}) - \sqrt{2}( \sqrt{5} + \sqrt{7} - \sqrt{2}) = \\ \\ 5 + \sqrt{35} - \sqrt{10} - \sqrt{35} - 7 + \sqrt{14} - \sqrt{10} - \sqrt{14} + 2 = \\ \\ (5 - 7 + 2) + ( \sqrt{35} - \sqrt{35}) + ( - \sqrt{10} - \sqrt{10}) + ( \sqrt{14} - \sqrt{14}) = \\ \\ - 2 \sqrt{10} [/tex]
