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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 10 May 2010, 16:45
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A
B
C
D
E

Difficulty:

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Question Stats:

65% (01:31) correct 35% (00:55) wrong based on 31 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: please help solve this for me [#permalink] New post 10 May 2010, 16:50
Its B

2x^2 -y^2 = 2xy
2x^2 = 2xy + y^2

Add x^2 on both sides we get

2x^2 +x^2 = x^2 +y^2 +2xy
3x^2 = (x+y)^2
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Re: please help solve this for me [#permalink] New post 10 May 2010, 16:53
Expert's post
bakfed wrote:
If 2x^2 - y^2 = 2xy, then (x+y)^2 =

A. x^2
B. 3x^2
C. 4xy
D. 2y^2
E. -y^2

OA
[Reveal] Spoiler:
B


Given: 2xy=2x^2-y^2.

(x+y)^2 =x^2+2xy+y^2 --> substitute 2xy --> (x+y)^2 =x^2+(2x^2 - y^2)+y^2=3x^2.

Answer: B.
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Re: please help solve this for me [#permalink] New post 18 May 2010, 08:17
bakfed wrote:
If 2x^2 - y^2 = 2xy, then (x+y)^2 =

A. x^2
B. 3x^2
C. 4xy
D. 2y^2
E. -y^2

OA
[Reveal] Spoiler:
B

here we have to find the value of x^2 +y^2 +2xy in which 2xy
=2x^2 -y^2 (given ) hence ans is 3x^2.
Re: please help solve this for me   [#permalink] 18 May 2010, 08:17
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