TT-3-28

lxj19820127

 

If x and y are integers and x > 0, is y > 0?

(1)     7x – 2y > 0

(2)     -y < x

                  

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.

答案E

luolihua73

 x>0

(1) x>(2/7)y

(2)x>-y

根据已知条件不能推出y 是大于0的整数

hmm,it should be E

lewis

(1)-->  y<(7/2）x
(2)-->  y>-x
so  -x < y < (7/2)x, 所以y不定

lewis

代入法,设定特殊值,不要试图找规律证明

叮叮当当

试一下X=2, Y=1; X=2, Y=-1