Need help with the explanations

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Need help with the explanations

by sochatte » Wed Dec 12, 2007 7:11 pm
Is x negative?

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

2. x^2 - 1 < 0

I need help with explanations...

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by samirpandeyit62 » Wed Dec 12, 2007 11:39 pm
Is x negative?

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

i.e x^3 -x^5 < 0

or x^3 < x^5

here x can be +ve like 2 & x can be -ve like -.2 INSUFF

2. x^2 - 1 < 0

or x^2 <1 i.e x <1> -1

again both -ve & +ve values are possible

INSUFF

Combine

x^3 < x^5 & x <1> -1

so x can be -1<x<0 to satisfy both the conditions

hence -ve SUFF C
Regards
Samir