下列图形中,既是轴对称图形,又是中心对称图形的是 ( ▲ )

A B C D
若 ,则
,则 的值为                                               
(  ▲  )
的值为                                               
(  ▲  )
A. B.
           B. C.
            
C. D.
            
D.
计算 ·
· 的结果是                                                             
(  ▲  )
的结果是                                                             
(  ▲  )
A. B.
            B. C.
             
C. D.
            D. 
                                        
 的绝对值等于                                                             
(  ▲  )
的绝对值等于                                                             
(  ▲  )
A. B.
             B. C.
            
C. D
           
D 
 
梯形的中位线长为3,上底长为2,则该梯形的下底长为 ▲ .
分解因式:m3—4m= ▲ .
