\[\boxed{\mathbf{984}\mathbf{.}}\]
\[1)\ F(x) = \frac{2}{x}\text{\ \ }и\ \ f(x) = - \frac{2}{x^{2}};\]
\[F^{'}(x) = 2 \bullet \left( \frac{1}{x} \right)^{'} = - \frac{2}{x^{2}} = f(x).\]
\[2)\ F(x) = 1 + \sqrt{x}\text{\ \ }и\ \ \]
\[f(x) = \frac{1}{2\sqrt{x}};\]
\[F^{'}(x) = (1)^{'} + \left( \sqrt{x} \right)^{'} =\]
\[= 0 + \frac{1}{2\sqrt{x}} = \frac{1}{2\sqrt{x}} = f(x).\]