\[\boxed{\mathbf{777}\mathbf{.}}\]
\[\mathbf{Н}а\ отрезке\ \lbrack 1\ 1,2\rbrack.\]
\[1)\ s(t) = 2t\]
\[v_{ср} = \frac{s\left( t_{2} \right) - s\left( t_{1} \right)}{t_{2} - t_{1}} =\]
\[= \frac{2 \bullet 1,2 - 2 \bullet 1}{1,2 - 1} = \frac{2,4 - 2}{0,2} =\]
\[= \frac{0,4}{0,2} = 2.\]
\[2)\ s(t) = t^{2}\ \]
\[v_{ср} = \frac{s\left( t_{2} \right) - s\left( t_{1} \right)}{t_{2} - t_{1}} = \frac{{1,2}^{2} - 1^{2}}{1,2 - 1} =\]
\[= \frac{1,44 - 1}{0,2} = \frac{0,44}{0,2} = 2,2.\]