Urèete derivaci funkce:
   $$
      y=2+x-x^2
   $$
   a vypoètìte $y'(0)$, $y'\left(\frac12\right)$, $y'(1)$, $y'(-10)$.

   \reseni
   \begin{align*}
      y'(x)                  & = 1 - 2x\\
      y'(0)                  & = 1     \\
      y'\left(\frac12\right) & = 0     \\
      y'(1)                  & = -1    \\
      y'(-10)                & = 21.
   \end{align*}
