\[\boxed{\mathbf{16}\mathbf{.}}\]
\[Если\ каждая\ из\ функций\ u_{1}(x);\]
\[u_{2}(x);\ldots;u_{n}(x)\ имеет\ в\ точке\ x\]
\[производную\ A_{1};A_{2};\ldots;\]
\[A_{n} - данные\ числа,\ то\ \]
\[справедливо\ равенство:\]
\[\left( A_{1}u_{1} + A_{2}u_{2} + \ldots + A_{n}u_{n} \right)^{'} =\]
\[= A_{1}u_{1}^{'} + A_{2}u_{2}^{'} + \ldots + A_{n}u_{n}^{'}.\]
\[n = 1:\]
\[\left( A_{1}u_{1} \right)^{'} = A_{1}u_{1}^{'}.\]
\[n = k:\]
\[\left( A_{1}u_{1} + A_{2}u_{2} + \ldots + A_{k}u_{k} + A_{k + 1}u_{k + 1} \right)^{'} =\]
\[= \left( A_{1}u_{1} + A_{2}u_{2} + \ldots + A_{k}u_{k} \right)^{'} +\]
\[+ \left( A_{k}u_{k} + A_{k + 1}u_{k + 1} \right)^{'} =\]
\[= A_{1}u_{1}^{'} + A_{2}u_{2}^{'} + \ldots + A_{k}u_{k}^{'} +\]
\[+ A_{k + 1}u_{k + 1}^{'}.\]
\[Что\ и\ требовалось\ доказать.\]