题目
If x and y are integers, is x2 – 1 > y2 + 1?
(1) x > y
(2) y > 0
选项
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.
Answer: C
注释:条件(1)(2)同时成立时,x>y>0,又因为x和y都是整数,所以为x2 – y2 ≥3,不等式成立。单独条件无法论证,如果x=2, y=-5,等式不成立,(1)不充分;当x=2, y=2,等式不成立,(2)不充分,所以选择C。
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