ChaseDream

标题: 求助一道GWD，感觉答案有误。。 [打印本页]

作者: owen870930 时间: 2010-10-7 06:08
标题: 求助一道GWD，感觉答案有误。。
Q7:

If x(x - 5)(x + 2) = 0, is x negative?

(1) x2 – 7x ≠ 0

(2) x2 –2x –15 ≠ 0

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.
答案给的是C~可是我觉得选B~
题目得出X=5或X=-2
条件2得出X≠5andX≠-3
所以X只有等于-2了~条件2充分~
而条件一得出X≠7根本没用·
我觉的就是答案错了把？

作者: chinamerica 时间: 2010-10-7 06:22
题目得出 X=0,5,-2
只有条件2，X可能等于0或者-2

作者: faybrilliance 时间: 2010-10-7 20:41
答案是对的，确实是C。因为题目中问的是negative，（1）决定了x不等于0, （2）使得其不为正数，加起来才能达到非负的要求

作者: 13873194104 时间: 2010-10-7 20:50
楼上正解实数解包括negative 0 and positive

作者: owen870930 时间: 2010-10-8 00:31
哦~明白了·原来忽略了X=0了·谢谢楼上几位的解释

欢迎光临 ChaseDream (https://forum.chasedream.com/)