4.
[tex]f(x) = \frac{2x-8}{x}\\\\f(\sqrt{2}) = \frac{2\cdot\sqrt{2}-8}{\sqrt{2}} = \frac{2\sqrt{2}}{\sqrt{2}}-\frac{8}{\sqrt{2}}\cdot\frac{\sqrt{2}}{\sqrt{2}} = 2-\frac{8\sqrt{2}}{2} = 2-4\sqrt{2}\\\\Odp. \ A.[/tex]
8.
[tex]f(x) = \frac{2x^{3}}{x^{4}+1}\\\\f(-\sqrt{2}) = \frac{2\cdot(-\sqrt{2})^{3}}{(-\sqrt{2})^{4}+1} = \frac{2\cdot(-\sqrt{2})^{2}\cdot(-\sqrt{2})}{4+1} = \frac{2\cdot2\cdot(-\sqrt{2})}{5} = -\frac{4\sqrt{2}}{5}\\\\Odp. \ C.[/tex]
