Odpowiedź:
[tex]2\sqrt{5}(\sqrt{5}-x)-3x(x^2-4\sqrt{5})=2\cdot5-2\sqrt{5}x-3x^3+12\sqrt{5}x=10+10\sqrt{5}x-3x^3\\\\\\dla\ \ x=-\sqrt{5}\\\\10+10\sqrt{5}x-3x^3=10+10\sqrt{5}\cdot(-\sqrt{5})-3\cdot(-\sqrt{5})^3=10-10\cdot5-3\cdot(-\sqrt{125})=\\\\=10-50+3\sqrt{125}=-40+3\sqrt{25\cdot3}=-40+3\cdot5\sqrt{3}=-40+15\sqrt{3}[/tex]
