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[tex]Sa~se~efectueze~: \\ \\ ( \sqrt[4]{7} +2)( \sqrt[4]{7} -2)( \sqrt{7} +4).[/tex]

Răspuns :


[tex]\it If\ \sqrt[4] 7 =a,\ then\ \sqrt7 = (\sqrt[4] 7)^2 = a^2 \\\;\\ So,\ we\ have :[/tex]

[tex]\it (a+2)(a-2)(a^2+4) =(a^2-4)(a^2+4) = a^4-16= (\sqrt[4]7)^4 -16 = \\\;\\ 7-16 = -9[/tex]