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by truplayer256 » Thu Feb 19, 2009 3:43 pm
(x+2y)^(2)=10xy
(x-2y)^(2)=2xy
x+2y=(10xy)^(1/2)
x-2y=(2xy)^(1/2)
x+2y/x-2y=sqrt10*sqrt(xy)/sqrt2*sqrt(xy)
sqrt(xy)'s cancel and you're left with sqrt10/sqrt2=sqrt5*sqrt2/sqrt2=sqrt5 (E)
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by cramya » Thu Feb 19, 2009 8:10 pm
Square numerator and denominator(since we are given value for x^2+4y^2)

x^2+4y^2+4xy / x^2+4y^2-4xy

= 6xy+4xy/6xy-4xy

= 5

Since we squared it now take the square root

sqrt(5)

Hence E
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