\[f(x) = 6 - 2x + x^{2};\ \ \ \]
\[y = 4x + a\]
\[1)\ Точка\ касания:\]
\[f^{'}(x) = 0 - 2 + 2x = 4;\]
\[2x = 6\]
\[x = 3.\]
\[f(3) = 6 - 6 + 9 = 9.\]
\[2)\ 4 \bullet 3 + a = 9\]
\[a = 9 - 12 = - 3.\]
\[Ответ:\ \ a = - 3;\ (3;\ 9).\]