GWD-2-gmat-8 请教，谢谢！

coolmanrays

GWD-2-gmat-8

Q8:

The operation Ä is defined for all nonzero numbers a and b by a Ä b = a/b – b/a. If x and y are nonzero numbers, which of the following statements must be true?

I. x Ä xy = x(1 Ä y)

II. x Ä y = -(y Ä x)

III. 1/x Ä 1/y = y Ä x

A. I only

B. II only

C. III only

D. I and II

E. II and III

Answer: E

请教，这道题怎么做呀？谢谢。

WalkByFaith

 Ä xy = x/xy-xy/x=1/y-y

不好意思，我還是有點不太懂

x/xy-xy/x是如何運算成1/y-y?

x(1 Ä y)=x*(1/y-y)這是如何形成的呢?

謝謝

sinadragon

放进公式a Ä b = a/b – b/a一个一个套呗，耐心点就可．

答案Ｅ没错

qingdaonycS

II和III里面的算了之后都相等，所以选E.

redemptioner

就是“Ä ”是一个符号，代表着这样一种运算规则~

把等式两边的都用这个规则换算一下~~看看是否相等就好啦~

像I中的x Ä xy = x/xy-xy/x=1/y-y

x(1 Ä y)=x*(1/y-y)

所以两边不相等啊