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标题: 这道GWD答案给错了吧 [打印本页]

作者: hebeqiao 时间: 2008-1-13 11:11
标题: 这道GWD答案给错了吧

Q32:结合条件1和2可知x,y,z 同号，那么有可能三者同正，则x (y + z) > 0;还可能三者同负，则x (y + z) < 0，应该选E, 答案却是C.

If xyz
≠ 0, is x (y + z) ≥ 0?

(1)
│y + z│ = │y│ + │z│

(2)
│x + y│ = │x│ + │y│

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.

作者: boston8899 时间: 2008-1-13 11:36
ans: C

作者: monacopig 时间: 2008-1-13 17:45
if x, y, z are all negative, x(y+z) is positive

作者: hebeqiao 时间: 2008-1-14 03:38
谢谢你，我真糊涂呀。

作者: jczephyr 时间: 2008-1-14 13:41
另，虽然题目问 is x (y + z) ≥ 0?，如果根据给定条件可以判定 ≥ 0 或肯定<0，都可以算作充分的吧。

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