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is x-y+1 greater than x+y-1?

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GMAT Fever
 Post subject: is x-y+1 greater than x+y-1?
 Post Posted: Sun Jun 15, 2008 7:49 pm 
is x-y+1 greater than x+y-1?

(1) x > 0
(2) y < 0

Can someone walk me through their systematic approach for this one? Thanks!
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Guest
 Post subject: Re: is x-y+1 greater than x+y-1?
 Post Posted: Mon Jun 16, 2008 3:00 am 
GMAT Fever wrote:
is x-y+1 greater than x+y-1?

(1) x > 0
(2) y < 0

Can someone walk me through their systematic approach for this one? Thanks!



(1) not enough
(2) not enough

1+2 enough because since when x>0 and y<0, any the first equation can be written as "x- (-y) +1" or x+y+1, which will always be greater than the same numbers minus 1.

Answer : C

Hope it helps.
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Guest
 Post subject:
 Post Posted: Mon Jun 16, 2008 6:25 pm 
reformat the question:

is x-y+1 > x+y-1
- take move x's and y's to one side and numbers to the other

is y <1

statement 1) doesnt tell us anything about Y
statement 2) if y<0 then y must be <1

B is the answer
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GMAT Fever
 Post subject: Re: is x-y+1 greater than x+y-1?
 Post Posted: Mon Jun 16, 2008 6:28 pm 
Guest wrote:
GMAT Fever wrote:
is x-y+1 greater than x+y-1?

(1) x > 0
(2) y < 0

Can someone walk me through their systematic approach for this one? Thanks!



(1) not enough
(2) not enough

1+2 enough because since when x>0 and y<0, any the first equation can be written as "x- (-y) +1" or x+y+1, which will always be greater than the same numbers minus 1.

Answer : C

Hope it helps.


GmatPrep has an answer of B.

I tried solving for X, then Statement 2 - B gives a definite answer. However when I solve for Y, Statement 1 - A gives a definite answer as well, however one that makes the two statements contradict each other which is always a no no!

So I guess I am still lost at finding a definitive approach for this problem.
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Guest
 Post subject:
 Post Posted: Mon Jun 16, 2008 7:10 pm 
you can't solve for x because it cancels itself out

when you see that x cancels itself out you will know that choice one is insignificant as x can be anything since it is on both sides of the equation.

you need to solve for y to simplify the equation.

even if you do nothing statement A should not give a definite answer.
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GMAT Fever
 Post subject:
 Post Posted: Mon Jun 16, 2008 10:26 pm 
Anonymous wrote:
reformat the question:

is x-y+1 > x+y-1
- take move x's and y's to one side and numbers to the other

is y <1

statement 1) doesnt tell us anything about Y
statement 2) if y<0 then y must be <1

B is the answer


Duh...total brain freeze, that makes total sense. Thanks!

Anonymous wrote:
you can't solve for x because it cancels itself out

when you see that x cancels itself out you will know that choice one is insignificant as x can be anything since it is on both sides of the equation.

you need to solve for y to simplify the equation.

even if you do nothing statement A should not give a definite answer.


Yea that was my problem, I was trying to solve as two separate equations when in fact I should have been solving for the whole inequality. Thanks!
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StaceyKoprince
 Post subject:
 Post Posted: Thu Jun 26, 2008 2:42 am 
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ManhattanGMAT Staff


Posts: 5788
Location: San Francisco
glad you guys figured it out without us! :)

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Stacey Koprince
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