Question

Cum calculez?........

Answer 1

Răspuns:

18

Explicație pas cu pas:

$E = \sqrt[3]{9+4\sqrt{5}} + \sqrt[3]{9-4\sqrt{5}}\Bigg | \hat{}\,\,3\\\\E^3 = 9 + 4\sqrt{5} + 9 - 4\sqrt{5} + 3\cdot \sqrt[3]{9+4\sqrt{5}}\sqrt[3]{9-4\sqrt{5}}\cdot E\\ \\ E^3 = 18 + 3\cdot \sqrt[3]{81 - 80}\cdot E\\ \\ E^3 = 18 + 3\sqrt[3]{1}\cdot E\\ \\ E^3 = 18 + 3E\\ \\ E^3 - 3E = \boxed{18}$