p a negative number

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Source: — Data Sufficiency |

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by mikeCoolBoy » Sun May 31, 2009 7:43 am
IMO C

rephrase the question is p < 0?

2)
p^2 – 1 < 0 ---> p^2 < 1 ----> -1 < p < 1

insufficient plug p = -1/2 and p = 1/2

1)

p^3(1 – p^2) < 0 ---> p^3 - P^5 <0 ---> p^3 < p^5

if p > 0 then p^3 < p^5 ---> 1 < p ^2 ---> p > 1
if p < 0 then p^3 < p^5 ----> 1 > p ^2 ----> -1 < p < 0

the solutions are p > 1 and -1 < p < 0
insufficient plug p = 2 and p = -1/2

Both statements together

2) -1 < p < 1
1) p > 1 and -1 < p < 0

the intersection of the two intervals is -1 < p < 0
sufficient