2.
[tex]2x-(x^{2}-5) = 2\cdot(-2) - ((-2)^{2}-5) = -4-(4-5) = -4-(-1) = -4+1 = -3\\\\Odp. \ B.[/tex]
3.
[tex]A. \ \frac{1}{2}(5x-10y)=\frac{1}{2}(5\cdot5 - 10\cdot\frac{1}{2}) = \frac{1}{2}(25-5) = \frac{1}{2}\cdot20 = 10\\\\B. \ 2x-2y+1 =2\cdot5-2\cdot\frac{1}{2}+1 =10-1+1 = 10\\\\\underline{C. \ \frac{1}{2}x + 15y-5 = \frac{1}{2}\cdot5+15\cdot\frac{1}{2}-5 = 2,5+7,5 -5 = 10-5 = 5 \neq 10}\\\\D. \ \frac{4}{9}(x-y)^{2}+1 = \frac{4}{9}(5-\frac{1}{2})^{2} + 1 = \frac{4}{9}(4\frac{1}{2})^{2}+1 = \frac{4}{9}(\frac{9}{2})^{2}+1 = \frac{4}{9}\cdot\frac{9\cdot9}{2\cdot2}+1 = 9+1 = 10\\\\Odp. \ C.[/tex]
