A:since
B:so that
C:as soon as
D:although.
(Ⅰ)求f(t)的单调减区间;
(Ⅱ)求证:f(t)+f(t+2)+f(t+4)是定值.
在横线上填上合适的数
6____7>657 3____49>3549 789>____98