Question

sa se verifice egalitatea!

Answer 1

Folosim formulele:

$(a+b)^3=a^3+b^3+3ab(a+b)$

$(a-b)(a+b)=a^2-b^2$

$\sqrt[3]{x^3}=x$

Ridicam la puterea a treia fiecare membru al egalitatii si obtinem o egalitate echivalenta:

$9+\sqrt{80}+9-\sqrt{80}+3\sqrt[3]{9^2-80}(\sqrt[3]{9+\sqrt{80}}+\sqrt[3]{9-\sqrt{80}})=3^3$

$18+3\cdot1\cdot3=27$

$27=27$