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If 2x^2 –y^2 = 2xy, then (x+y)^2=

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If 2x^2 –y^2 = 2xy, then (x+y)^2= [#permalink] New post 11 Nov 2010, 21:38
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Question Stats:

81% (02:12) correct 19% (02:43) wrong based on 105 sessions
If 2x^2 –y^2 = 2xy, then (x+y)^2=

(A) X^2
(B) 3x^2
(C) 4xy
(D) 2y^2
(E) –y^2
[Reveal] Spoiler: OA

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Re: If 2x^2 –y^2 = 2xy [#permalink] New post 11 Nov 2010, 23:21
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Re: If 2x^2 –y^2 = 2xy [#permalink] New post 12 Nov 2010, 13:46
2x^2 –y^2 = 2xy
2x^2 = 2xy+y^2

3x^2 = x^2 + 2xy+y^2 (adding x^2 on both sides)

3x^2 = (x+y)^2


Answer:- B
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Re: If 2x^2 –y^2 = 2xy [#permalink] New post 12 Nov 2010, 16:30
2x\(^2\)-y\(^2\)=2xy

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

replace 2xy by 2x\(^2\)-y\(^2\) and solve

Answer B.
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Re: If 2x^2 –y^2 = 2xy [#permalink] New post 29 Dec 2010, 12:08
Sarang wrote:
2x^2 –y^2 = 2xy
2x^2 = 2xy+y^2

3x^2 = x^2 + 2xy+y^2 (adding x^2 on both sides)

3x^2 = (x+y)^2


Answer:- B


i didn't understand this pls explain
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Re: If 2x^2 –y^2 = 2xy [#permalink] New post 29 Dec 2010, 12:33
Expert's post
rahul321 wrote:
Sarang wrote:
2x^2 –y^2 = 2xy
2x^2 = 2xy+y^2

3x^2 = x^2 + 2xy+y^2 (adding x^2 on both sides)

3x^2 = (x+y)^2


Answer:- B


i didn't understand this pls explain


Given: \(2x^2-y^2=2xy\) --> rearrange: \(2x^2=2xy+y^2\) --> add \(x^2\) to both parts of the equation: \(2x^2+x^2=x^2+2xy+y^2\) --> \(3x^2=(x+y)^2\).

Hope it's clear.
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If 2x^2 –y^2 = 2xy, then (x+y)^2= [#permalink] New post 17 Jul 2014, 01:42
\(2x^2 – y^2 = 2xy\)

so, \(y^2 = 2x^2 - 2xy\) ............ (1)

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

Placing value of \(y^2\) from (1)

\(= x^2 + 2xy + 2x^2 - 2xy\)

\(= 3x^2\)

Answer = B
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Re: If 2x^2 –y^2 = 2xy, then (x+y)^2= [#permalink] New post 20 Jul 2015, 19:33
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Re: If 2x^2 –y^2 = 2xy, then (x+y)^2= [#permalink] New post 21 Jul 2015, 07:38
\(2x^2 - y^2 = 2xy\)

\((x+y)^2 = x^2 + 2xy + y^2 = x^2 + 2x^2 - y^2 + y^2 = 3x^2\). Ans (B).
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Re: If 2x^2 –y^2 = 2xy, then (x+y)^2=   [#permalink] 21 Jul 2015, 07:38
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