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Is x² - y > 1/y²

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Source: — Data Sufficiency |
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by iamseer » Sun May 09, 2010 11:30 am
Since y^2 is >0 we can cross multiply.

from 1:
x,y, Is (y^2*x^2-Y^3)>1?
2,3, Is (36-27)>1 Yes
0.1,0.2 (everything less than 1) NO
Not Sufficient

from 2:
x^2,y^2, Is (y^2*x^2-Y^3)>1?
take x=sqrt2 and y=sqrt3
2,3, Is (36-27)>1 Yes
take x=0.1, y=0.2
0.01,0.04 (everything less than 1) NO
Not Sufficient

Combining 1 and 2:
examples in St2 are in fact combining both 1 and 2
Not Sufficient

IMO answer E
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