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# What is the value of x^2 + y^2? (1) x^2 + y^2 = 2xy +1 (2)

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Joined: 25 Nov 2006
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Schools: St Gallen, Cambridge, HEC Montreal
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What is the value of x^2 + y^2? (1) x^2 + y^2 = 2xy +1 (2) [#permalink]  28 Jan 2009, 10:57
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What is the value of x^2 + y^2?

(1) x^2 + y^2 = 2xy +1

(2) x^2 + y^2 = 4 - 2xy
Senior Manager
Joined: 30 Nov 2008
Posts: 493
Schools: Fuqua
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Re: DS question [#permalink]  28 Jan 2009, 11:22
IMO C.

From Stmt 1, we can derive, x^2+ y^2-2xy = 1 ==> cannot say the value for x^2 + y^2 with this information. In Sufficient.
From Stmt 2, we can derive, x^2+ y^2+2xy = 4 ==> cannot say the value for x^2 + y^2 with this information. In Sufficient.

Now combining both the equations, two unknowns and two equations, definitely we can solve both the eqs to get the value of x and y from which we can get the value x^2 + y^2.

Well the value of x^2 + y^2 = 5/2.
Re: DS question   [#permalink] 28 Jan 2009, 11:22
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