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by parallel_chase » Sat Nov 29, 2008 7:38 am
2x^2 - y^2 = 2xy

2x^2 = 2xy + y^2


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

we can substitute the value of y^2 + 2xy

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

Hope this helps.
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by cramya » Sat Nov 29, 2008 11:26 am
Similar approach

2x^2-y^2=2xy 1)

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

=x^2+y^2+(2x^2-y^2) from (1) 2xy=2x^2-y^2
=3x^2