\[f(x) = 4x - 2x^{2}\]
\[x_{0} = \frac{- 4}{- 4} = 1;\ \ y_{0} = 2\]
\[f(x) \leq 0\ \ при\ \ \ \ x \leq 0\ \ и\ \ x \geq 2;\]
\[f(x) > 0\ \ \ при\ \ \ \ 0 < x < 2.\]