滔滔 - GWD-1-6

Sunshine2008

    

If x and y are positive, what is the value of x – y?

    

(1)
          (x² – y²)
/ (x + y) = 4

    

(2)
          x + y
        = 7

    

                  

    

A. Statement (1) ALONE is sufficient, but statement
(2) alone is not sufficient.

    

B. Statement (2) ALONE is sufficient, but statement
(1) alone is not sufficient.

    

C. BOTH statements TOGETHER are sufficient,
but NEITHER statement ALONE is sufficient.

    

D. EACH statement ALONE is sufficient.

    

E. Statements (1) and (2) TOGETHER are NOT
sufficient.

My Answer is C, but OA is A.

No discussion can be found on this one.

I dun believe I am wrong. But I am curious why this is no dispute on the answer at all.

有高人可以释惑吗?

crackingkiko

第一个条件就可以了,(x+y)(x-y)/(x+y)=4

第2个条件不可以

Sunshine2008

倒，原来是我把第一个条件看成(x² – y²) * (x + y) = 4.
在此谢过crackingkiko mm.

jw5094

  

   <X平方-Y平方>/X+Y=4

可化为 <X+Y><X-Y>/X+Y=4

分式同时约<X+Y>,得<X-Y>=4

所以A 为正确答案