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another problem

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Junior | Next Rank: 30 Posts
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another problem

by elimenda » Fri Nov 14, 2008 5:45 am
if 2x^2 -y^2 = 2xy, then, (x+y)^2=

1. x^2
2. 3x^2
3. 4xy
4. 2y^2
5. -y^2
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by cramya » Fri Nov 14, 2008 5:50 am
Given 2x^2 -y^2 = 2xy

i.e y^2 = 2x^2 - 2xy

Expand (x+y) ^ 2 = x^2 + y ^2 + 2xy (1) [(a+b)^2 = a^2+b^2+2ab]

Substitute 2x^2 - 2xy for y^2 IN (1)

= x^2+2x^2-2xy+2xy (-2XY+2XY=0)
= 3x^2

B)
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Junior | Next Rank: 30 Posts
Posts: 19
Joined: Fri Jul 11, 2008 10:26 am

by elimenda » Fri Nov 14, 2008 6:01 am
that was so fast!! tks!
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