1.
[tex]dla \ \ x = \frac{1}{2}\\\\20x^{2}-36x = 20\cdot(\frac{1}{2})^{2}-36\cdot\frac{1}{2} = 20\cdot\frac{1}{4}-18 = 5-18 = -13[/tex]
2.
[tex]dla \ \ x = -2\\\\x\cdot(5x-2)-2x\cdot(3x-4) = -2\cdot(5\cdot(-2)-2) - 2\cdot(-2)\cdot(3\cdot(-2)-4) =\\\\=-2\cdot(-10-2)+2(-6-4) =\-2\cdot(-12)+4\cdot(-10) = 24-40 = -16[/tex]
