prep 1 - DS 129

mauricew

Is (x+1)/(x-3)< 0?

(1) -1 < x < 1

(2) x^2 - 4 < 0
Answer: a
请问式子要怎麽列？

zuodun

[1](x+1)/(x-3)< 0 对与他可看成 x！=3 且(x+1)*(x-3)< 0，

[2](x+1)*(x-3)< 0又可以看成 x+1>0且x-3<0 或者  x+1<0且x-3>0 这两部分

综合[1][2]可以解得-1<x<3

条件二可以求得-2<x<2

答案自然就是a了

bth

Is (x+1)/(x-3)< 0?

(1) -1 < x < 1

(2) x^2 - 4 < 0
Problem Stem:

(x+1)/(x-3) will be less than zero only if x is between -1 and 1.

Stem1:

SUFF as it is saying that x is between -1 and 1.

Stem2:

x^2<4

=> x<+/-2 NOT SUFF.

Anaswer is A.