\[\boxed{\mathbf{11}\mathbf{.}}\]
\[f(x) = x^{2} - 6x + 11\]
\[\textbf{а)}\ f^{'}(x) = \left( x^{2} - 6x + 11 \right)^{'} =\]
\[= \left( x^{2} \right)^{'} - 6(x)^{'} + (11)^{'} =\]
\[= 2x^{2 - 1} - 6 \cdot 1 + 0 = 2x - 6.\]
\[\textbf{б)}\ tg\ a = f^{'}( - 1) = 2 \cdot ( - 1) -\]
\[- 6 = - 2 - 6 = - 8;\]
\[tg\ a = f^{'}(0) = 2 \cdot 0 - 6 = - 6;\]
\[tg\ a = f^{'}(2) = 2 \cdot 2 - 6 =\]
\[= 4 - 6 = - 2.\]
\[\textbf{в)}\ f^{'}(x) = 0:\]
\[2x - 6 = 0\]
\[2x = 6\]
\[x = 3.\]
\[f^{'}(x) = 1:\]
\[2x - 6 = 1\]
\[2x = 7\]
\[x = 3,5.\]
\[f^{'}(x) = 3:\]
\[2x - 6 = 3\]
\[2x = 9\]
\[x = 4,5.\]