\[y = x^{3} - x + 1;\]
\[x_{0} = 0;\]
\[y^{'}(x) = \left( x^{3} \right)^{'} - x^{'} - 1^{'} =\]
\[= 3x^{2} - 1;\]
\[y^{'}\left( x_{0} \right) = 3 \bullet 0^{2} - 1 =\]
\[= 0 - 1 = - 1.\]
\[Ответ:\ \ k = - 1.\]