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Data Sufficiency Question

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Source: — Problem Solving |

by vikram4689 » Fri May 13, 2011 7:02 pm
ans is C

i) x = -1 , n =1 , -3x is positive
ii) x = -1 , n =2 , -3x is negative
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by Tani » Fri May 13, 2011 8:00 pm
for -3x^n to be positive, x^n must be negative.

For that to be true, x must be negative and N must be a positive odd integer

We are told that x is negative and n is odd, however, we are not told that n is positive, so my answer would be E.
Tani Wolff
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by vikram4689 » Sat May 14, 2011 9:02 am
Hi Tani ,

I do not think it matters whether N is positive or negative. In case of negative N , fraction would be reciprocal of earlier fraction but positivity or negativity of x^n would remain intact.

x =-1 n =3 , x^n = (-1)^3 = -1
x =-1 n =-3 , x^n = (-1)^(-3) = 1/(-1)^3 = 1/-1= -1
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