\[\boxed{\mathbf{845}\mathbf{.}}\]
\[1)\ f(x) = {0,5}^{x} \bullet \cos{2x}\]
\[2)\ f(x) = 5\sqrt{x} \bullet e^{- x}\]
\[= 5e^{- x} \bullet \left( \frac{1}{2\sqrt{x}} - \sqrt{x} \right) =\]
\[= 5e^{- x} \bullet \frac{1 - 2x}{2\sqrt{x}} =\]
\[= \frac{5}{2\sqrt{x}} \bullet (1 - 2x) \bullet e^{- x}.\]
\[3)\ f(x) = e^{3 - 2x} \bullet \cos(3 - 2x)\]