GWD23-Q6

nicboy

    

Q6:

    

The operation Θ is defined by x Θ y =  +  for all nonzero
numbers x and y.  If z
is a number greater than 1, which of the following must be true?

    

                                                           

    

 

    

  I.  x Θ (-z)
= 0

    

       II.  z
Θ (z/(z-1)) = 1

    

      III. 
2/z Θ 2/z  = z

    

 

    

 

    

A.  I only

    

B.  I and II only

    

C.  I and III
only

    

D.  II and III
only

    

E.  I, II, and
III

    

 
Answer:   (D)

为什么是D呀，第一个是等于0啊，谁帮忙看一看，谢谢

[此贴子已经被作者于2008-7-16 16:48:35编辑过]