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Number properties 10 Jan 2012, 23:57
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C
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I tried with various numbers it was giving Yes or No answers....but surprisingly the answer is C.........can anyone explain this please........



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LalaB
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Number properties 11 Jan 2012, 00:34
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hm, strange that stmnts contradict each other. I mean first we are said, that (x-y)^2=8. but in stmnt (2) the same equity is equal to 10...strange
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Number properties 11 Jan 2012, 01:18
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Really strange. Must be something wrong with question
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Number properties 11 Jan 2012, 01:21
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kotela
I tried with various numbers it was giving Yes or No answers....but surprisingly the answer is C.........can anyone explain this please........
Show more

Here's the solution I came up with,

1 ..not sufficient cuz the expansion would never give us xy
2 ..same as 1

(x-y) squared= xsquare+ y square - 2xy = 8
x-y squared = xsquare + y Square - 2xy = 10 ,
becomes
-2xy= 8- xsquare-ysquare
-2xy = 10- xsquare - y square
solve simultaneously by adding both equations
-4xy = 18 -2xsquare - 2ysquare...divide both sides by -2
2xy = 9 + x square + y square
xy =(9+ x square + y square) divided by 2

We know x square + y square can not be negative. Thus, xy will always be greater than 0.

Ans . C
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Number properties 11 Jan 2012, 03:58
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onayemi
kotela
I tried with various numbers it was giving Yes or No answers....but surprisingly the answer is C.........can anyone explain this please........

Here's the solution I came up with,

1 ..not sufficient cuz the expansion would never give us xy
2 ..same as 1

(x-y) squared= xsquare+ y square - 2xy = 8
x-y squared = xsquare + y Square - 2xy = 10 ,
becomes
-2xy= 8- xsquare-ysquare
-2xy = 10- xsquare - y square
solve simultaneously by adding both equations
-4xy = 18 -2xsquare - 2ysquare...divide both sides by -2
2xy = 9 + x square + y square
xy =(9+ x square + y square) divided by 2

We know x square + y square can not be negative. Thus, xy will always be greater than 0.

Ans . C
Show more

But but X and Y can be negative -ve * -ve ==positive and (-x)^2 = +ve but here X can be -ve or +Ve and same is the case with Y..........Can you how you assumed X and Y to be positive...i agree that X^2 and Y^2 is positive but X and Y can be -Ve or +Ve .........Please correct me if i am wrong
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Number properties 11 Jan 2012, 04:11
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onayemi
kotela
I tried with various numbers it was giving Yes or No answers....but surprisingly the answer is C.........can anyone explain this please........

Here's the solution I came up with,

1 ..not sufficient cuz the expansion would never give us xy
2 ..same as 1

(x-y) squared= xsquare+ y square - 2xy = 8
x-y squared = xsquare + y Square - 2xy = 10 ,
becomes
-2xy= 8- xsquare-ysquare
-2xy = 10- xsquare - y square
solve simultaneously by adding both equations
-4xy = 18 -2xsquare - 2ysquare...divide both sides by -2
2xy = 9 + x square + y square
xy =(9+ x square + y square) divided by 2

We know x square + y square can not be negative. Thus, xy will always be greater than 0.

Ans . C
Show more
When you divided by -2 you forgot to divide 18 by -2 ... WINK WINK ! :)
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omerrauf
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Number properties 11 Jan 2012, 04:13
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There is a problem with the question. The answer to the question posted, as is, would have to be E.....



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Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
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