[tex] \sqrt{7}(\sqrt{7} - \sqrt{6} )+ \sqrt{6} ( \sqrt{7} - \sqrt{6} )= \\ \\ ( \sqrt{7} + \sqrt{6} )( \sqrt{7} - \sqrt{6} )= \\ \\ ( \sqrt{7})^{2} -( \sqrt{6})^{2}= \\ \\ 7-6=1 [/tex]
SAU
[tex]\sqrt{7}(\sqrt{7} - \sqrt{6} )+ \sqrt{6} ( \sqrt{7} - \sqrt{6} )=
\\ \\ (\sqrt{7}) ^{2}- \sqrt{42} + \sqrt{42} -( \sqrt{6} )^{2}= \\ \\ (
\sqrt{7})^{2}- (\sqrt{6})^{2}= \\ \\ 7-6=1 [/tex]