\[\boxed{\mathbf{896}\mathbf{.}}\]
\[y = ax - 2f(x) = 1 + \ln x\]
\[f^{'}\left( x_{0} \right) = (1)^{'} + \left( \ln x \right)^{'} =\]
\[= 0 + \frac{1}{x} = \frac{1}{x_{0}}\]
\[f\left( x_{0} \right) = 1 + \ln x_{0}\]
\[y = 1 + \ln x_{0} + \frac{1}{x_{0}} \bullet \left( x - x_{0} \right) =\]
\[= 1 + \ln x_{0} + \frac{x}{x_{0}} - 1 =\]
\[= \frac{x}{x_{0}} + \ln x_{0}.\]
\[x_{0}:\]
\[\ln x_{0} = - 2\]
\[\ln x_{0} = \ln e^{- 2}\]
\[x_{0} = \frac{1}{e^{2}}.\]
\[a = \frac{1}{x_{0}} = 1\ :\frac{1}{e^{2}} = e^{2}.\]
\[Ответ:\ \ a = e^{2}.\]