[tex]\it 12-6\sqrt3=9+3-6\sqrt3=3^2-6\sqrt3+(\sqrt3)^2=(3-\sqrt3)^2\\ \\ Analog:\\ \\ 12+6\sqrt3=(3+\sqrt3)^2\\ \\ 6+4\sqrt2=(2+\sqrt2)^2\\ \\ 6-4\sqrt2=(2-\sqrt2)^2[/tex]
[tex]\it Folosind\ formula\ \sqrt{a^2}=a,\ \forall a>0,\ vom\ avea:\\ \\ x=3-\sqrt3+3+\sqrt3+2+\sqrt2-2+\sqrt2-2\sqrt2=6\in\mathbb{N}[/tex]