another/better way to solve :

1.

\(x^3(1-x^2)<0\)

for above term to be -ve , either \(x^3\) or \((1-x^2)\) will be negative . Both can not have the same sign.

However there is no way to find out which one is -ve and so no way to check the sign of x

INSUFFICIENT.

2.

\(x^2-1<0\)

\(x^2<1\)

x can lie in the range -1 to 1.

INSUFFICIENT.

TOGETHER:

from 1.

either \(x^3\) or \((1-x^2)\) will be negative

from 2.

x lies in the range -1 to 1 so \((1-x^2)\) can not be -ve.

Hance \(x^3\) is -ve and hance x is -ve.

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Lahoosaher