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# If 2x^2 –y^2 = 2xy

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If 2x^2 –y^2 = 2xy [#permalink]  11 Nov 2010, 22:38
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If 2x^2 –y^2 = 2xy, then (x+y)^2=

(A) X^2
(B) 3x^2
(C) 4xy
(D) 2y^2
(E) –y^2
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Re: If 2x^2 –y^2 = 2xy [#permalink]  12 Nov 2010, 00:21
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monirjewel 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

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

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Re: If 2x^2 –y^2 = 2xy [#permalink]  12 Nov 2010, 14:46
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

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Re: If 2x^2 –y^2 = 2xy [#permalink]  12 Nov 2010, 17:30
2x^2-y^2=2xy

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

replace 2xy by 2x^2-y^2 and solve

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Re: If 2x^2 –y^2 = 2xy [#permalink]  29 Dec 2010, 13:08
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

i didn't understand this pls explain
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Re: If 2x^2 –y^2 = 2xy [#permalink]  29 Dec 2010, 13:33
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

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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Re: If 2x^2 –y^2 = 2xy   [#permalink] 29 Dec 2010, 13:33
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