\[\boxed{\mathbf{924}\mathbf{.}}\]
\[1)\ a = - 2,\ \ \ b = 4:\ \ \ \]
\[f( - 2) = - 2,\ \ \ \]
\[f(x) = x\ при\ 1 \leq x \leq 4;\]
\[y = f(x)\ возрастает\ \]
\[на\ отрезке\ \lbrack - 2;\ 1\rbrack;\]
\[2)\ a = 1,\ \ \ b = 7:\ \ \ \]
\[f(7) = 1,\ \ \ \]
\[f(x) = x^{2}\ при\ 1 \leq x \leq 2;\]
\[y = f(x)\ убывает\ \]
\[на\ промежутке\ (2;\ 7\rbrack;\]