Răspuns :
obtinem 7 - 2 = 5
dar daca vrei demonstratie:
[tex]( \sqrt{7} - \sqrt{2} )( \sqrt{7} + \sqrt{2} )=\sqrt{7} ^{2} + \sqrt{7} \sqrt{2} - \sqrt{2} \sqrt{7} - \sqrt{2} ^{2} = \sqrt{7} ^{2} - \sqrt{2} ^{2} [/tex] = 7 - 2 = 5
dar daca vrei demonstratie:
[tex]( \sqrt{7} - \sqrt{2} )( \sqrt{7} + \sqrt{2} )=\sqrt{7} ^{2} + \sqrt{7} \sqrt{2} - \sqrt{2} \sqrt{7} - \sqrt{2} ^{2} = \sqrt{7} ^{2} - \sqrt{2} ^{2} [/tex] = 7 - 2 = 5