一道DS题, 比较迷惑both together 含义啊,,,是否要求交集??请高人指点

Arliscure

Q7:
What is the value of │x + 7│?
(1)     │x+ 3│= 14
(2)     (x +2)² = 169
                 
A. Statement (1) ALONE issufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE issufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHERare sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE issufficient.
E. Statements (1) and (2) TOGETHERare NOT sufficient.


计算过程
(1)得出x+3=14or-14 即 x=11 or-17
(2)得出x+2=13 or -13 即x=-15 or 11
答案说选C, 但是both together 是 x=11 -15 or -17啊,


很迷惑, 以前做到的题感觉没有 together 就是球交集的啊,,


谢谢

gmatbenben

both..together 是交集

either...or 是并集

Arliscure

顶一个

Arliscure

真的么, 以后这类 1,2 条件各给出集中答案的就求交集?

gmatbenben

真的. 多给一个例子:

问: what is the remainder of n divided by A?
条件:
1. the remainder of n divided by B is M;
2. the remainder of n divided by C is N.
解决问题:
列出符合条件1的数列,
列出符合条件2的数列,
假设我们找出两个数列"共有"的数值,组成新的数列.新的数列可以确认问题,那么就选C. BOTH statements TOGETHERare sufficient, but NEITHER statement ALONE is sufficient.
很明显, C是交集的意思.

sdcar2010

It is not about 交集.  It is about when combining the two conditions together, you can have sufficient conditions to solve the problem!

gmatbenben

you're right, sdcar.

if the concept of "union" and "intersection" helps Arliscure figure out how to solve this type of questions, let it be. :-)

Arliscure

THX

Arliscure

It is not about 交集.  It is about when combining the two conditions together, you can have sufficient conditions to solve the problem!

-- by 会员 sdcar2010 (2010/12/23 22:34:17)

THX, 但是还是没搞懂, combining 就确定了此题中的X只能是 11?

lijiesjtu

both and就意味着，x要同时满足1和2这两个条件，那么它只有一个可能，就是等于11