please help solve this for me

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please help solve this for me [#permalink]

10 May 2010, 17:45

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Question Stats:

60% (01:31) correct

40% (01:18) wrong

based on 10 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

OA

[Reveal] Spoiler:

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Re: please help solve this for me [#permalink]

10 May 2010, 17:50

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]

10 May 2010, 17:53

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:

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]

18 May 2010, 09:17

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:

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, 09:17

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please help solve this for me

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