\[\boxed{\mathbf{29}\mathbf{.}}\]
\[f^{'}(x) = u^{'}(x) \cdot v(x) + u(x) \cdot v^{'}(x)\]
\[y = Cf(x);\ \ C - константа:\]
\[y^{'}(x) = C^{'}f(x) + Cf^{'}(x) =\]
\[= 0 \cdot f(x) + Cf^{'}(x) = Cf^{'}(x).\]