\[От\ t_{1} = 2\ до\ t_{2} = 8.\]
\[1)\ s(t) = 2t + 1:\]
\[v = \frac{s(8) - s(2)}{8 - 2} =\]
\[= \frac{(16 + 1) - (4 + 1)}{6} = \frac{12}{6} = 2;\]
\[s^{'}(t) = 2;\]
\[v(2) = v(8) = 2.\]
\[Ответ:\ \ 2.\]
\[2)\ s(t) = 0,3t - 1:\]
\[v = \frac{s(8) - s(2)}{8 - 2} =\]
\[= \frac{(2,4 + 1) - (0,6 + 1)}{8 - 2} =\]
\[= \frac{1,8}{6} = 0,3;\]
\[s^{'}(t) = 0,3;\]
\[v(2) = v(8) = 0,3.\]
\[Ответ:\ \ 0,3.\]