inequality

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inequality

by thegmatbeater » Tue Jul 22, 2008 11:53 pm
If x is not equal to y

(x-y)/ (x+y) > 1 ?

1) x>0
2)y<0

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by msd_2008 » Wed Jul 23, 2008 12:16 am
Is the answer E?
When the going gets tough, the tough gets going.

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by reachac » Wed Jul 23, 2008 5:10 am
IMO C

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by cubicle_bound_misfit » Wed Jul 23, 2008 6:54 am
IMO it is B.

Please let me know OA.

my approach.
We gotta prove is x-y>x+y ?

i.e. is -y>y

stmt 2 SUFF.

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by jsl » Wed Jul 23, 2008 7:28 am
cubicle_bound_misfit wrote:We gotta prove is x-y>x+y
When you multiply an inequality, you need to be certain of the sign. If x+y is negative, the sign is reversed.... so I don't think you can do this since we can't be sure of the sign.

Would be interested in the OA though. I need a methodical way of working this one out!

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by nikhilagrawal » Wed Jul 23, 2008 9:56 am
I think "cubicle_bound_misfit" i correct in solving the eqn.
The eqn can be reduced to 2y < 0 or y <0

so answer shld be B .

Pls correct me if I am going fundamentally wrong in soloving the equation.

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by Canman » Wed Jul 23, 2008 11:23 am
I think jsl brings up a good point to remember about signs and direction of inequality when cross multiplying. But I also agree with some of the other posters and think B is sufficient.

To simplify the "rephrase" of the questions stem asks: "Is y>0 or is y<0?" (factoring in that the unknown signs can flip the inequality)

1) tells us nothing about y - insufficient
2) tells us y<0 - SUFFICIENT

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by cubicle_bound_misfit » Wed Jul 23, 2008 11:27 am
hi JSL,

the way I tried it

if x-y/x+y is > 1 then both denominator and numerator both has to be either greater than zero or less than zero.

in both the cases if you pick numbers , multiplying expression by denominator does not invert ineqalities.

Please let me know if I am wrong and what's the OA?

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by Canman » Wed Jul 23, 2008 12:04 pm
Actually I'm rethinking this going back through it with a common sense check by picking some numbers... maybe I've overthought the problem by trying to solve it with algebra

Maybe 2) y<0 isn't so sufficient after all.

Consider x=3, y=-1
Stem eqn will equal 2 which is a "YES" answer

Consider x=3, y=-4
Stem eqn will equal -1 which is a "NO" answer

Statement 1) suffers the same conclusion, as well as the statements together.

Could E be the answer after all?

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by Canman » Thu Jul 24, 2008 4:55 am
I checked and the OA on this is E.