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Guest
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 Posted: Sun Sep 30, 2007 1:17 pm Post subject: algebra DS |
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Not sure what to do with following
if 0<x<y what is the value of (x+y)^2/(x-y)^2
(1) x^2+y^2=3xy
(2) xy=3 |
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Guest
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| Posted: Sun Sep 30, 2007 1:20 pm Post subject: |
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| By the way, that question was from gmat prep. and answer was A. |
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kajcha
GMAT Destroyer!
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| Posted: Sun Sep 30, 2007 2:04 pm Post subject: |
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Ans would be A
(x+y)^2 = x^2+y^2+2xy ----------(1)
(x-y)^2 = x^2+y^2-2xy ------------(2)
you need to find (1)/(2)
stmt 1 - x^2+y^2 = 3xy
(1) will be 3xy+2xy = 5xy
(2) will be 3xy-2xy = xy
(1)/(2) = 5 SUFF
Stmt 2 - xy= 3. No info to calculate x^2+y^2 so NOT SUFF
Ans A |
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Guest
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| Posted: Mon Oct 01, 2007 7:07 pm Post subject: |
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| kajcha wrote: | Ans would be A
(x+y)^2 = x^2+y^2+2xy ----------(1)
(x-y)^2 = x^2+y^2-2xy ------------(2)
you need to find (1)/(2)
stmt 1 - x^2+y^2 = 3xy
(1) will be 3xy+2xy = 5xy
(2) will be 3xy-2xy = xy
(1)/(2) = 5 SUFF
Stmt 2 - xy= 3. No info to calculate x^2+y^2 so NOT SUFF
Ans A |
wow..so simple!!! and I was trying all kinds of manupilations...such as expanding denominator as product of difference of squares and canceling (x+y) in both numerator and denominator leaving x+y/x-y in denominator and was stuck... |
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