\[\boxed{\mathbf{906}\mathbf{.}}\]
\[1)\ a = - 2,\ \ \ b = 6:\ \ \ \]
\[f( - 2) = 1,\ \ \ \]
\[f(6) = 5,\ \ \ \]
\[f(3) = 0,\ \ \ \]
\[f^{'}(3) = 0;\]
\[f^{'}(x) < 0\ при - 2 < x < 3;\ \ \ \]
\[f^{'}(x) > 0\ при\ 3 < x < 6.\]
\[2)\ a = - 3,\ \ \ b = 3:\ \ \ \]
\[f( - 3) = - 1,\ \ \ \]
\[f(3) = 4,\ \ \ \]
\[f^{'}(2) = 0;\]
\[f^{'}(x) < 0\ при\ - 3 < x < 2;\ \ \]
\[f^{'}(x) > 0\ при\ 2 < x < 3.\]