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Aratati ca nr. a= |√5-√7|+ 2 supra √7-√5-√28 este intreg.

Răspuns :

[tex]a=|\sqrt5-\sqrt7|+\frac{2}{\sqrt7-\sqrt5}-\sqrt{28}\\ a=\sqrt7-\sqrt5+\frac{2(\sqrt7+\sqrt5)}{7-5}-2\sqrt7\\ a=\sqrt7-\sqrt5+\sqrt7+\sqrt5-2\sqrt7\\ \boxed{\bold{a=0\in \mathbb{Z}}}[/tex]