Is x negative?
(1) X^3(1-x^2) <0
(2) x^2-1<0
I have tried it as follows:
Stem1:
Either x^3 or (1-x^2) is -ve.
If x^3 is -ve, then x is -ve.
If 1-x^2 is -ve, then x^2>1, then x may be -ve or +ve. NOT SUFF.
Stem2:
x^2-1 is -ve means 1-x^2>0. X may be -ve or +ve. NOT SUFF.
1+2:
From 2 as 1-x^2>0, x^3 in one 1 is -ve.
So, x is -ve. SUFF.
Answer is C.
Is there any shorcut?
| 欢迎光临 ChaseDream (https://forum.chasedream.com/) | Powered by Discuz! X3.3 |