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calculează: [tex] \frac{1}{2 + \sqrt{5} }
[/tex] + [tex] \frac{1}{2 - \sqrt{5} }
[/tex]


Răspuns :



[tex] \frac{1}{2+ \sqrt{5} } + \frac{1}{2- \sqrt{5} } =\\\\ \frac{2+ \sqrt{5}+2- \sqrt{5} }{2^2- \sqrt{5}^2 }=\\\\ \frac{4}{4-5} =\\\\ \frac{4}{-1} =-4[/tex]

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