A.ab＜b²＜1                                     B.b＜a＜0

C.2^b＜2^a＜2                                     D.a²＜ab＜1

A.                 B.                 C.                 D.

A.-2                   B.2                    C.-4                  D.4

A.[-2，-1]              B.[-2，1]              C.[-1，2]              D.[1，2]

A.18                  B.36                      C.54                     D.72

A.(-4,)                                        B.(4,)

C.（-8，1）                                      D.（8，1）

A.充分而不必要条件                             B.必要而不充分条件

C.充要条件                                     D.既不充分也不必要条件

A.(0,2］                B.[0，2]                C.［-1,2)                D.

(1)求f(x)的表达式和极值.

(2)若f(x)在区间［m,m+4］上是单调函数,试求m的取值范围.

(3)存在正数t,使得对任意x₁,x₂∈［-t,t］,|f(x₁)-f(x₂)|≤27恒成立,试求t的取值范围.