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2015-06-27T19:13:09+05:30

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Is that 4x^2+9y^2 

y=2/x 

2x+3(2/x) = 8 

2x + 6/x = 8 
2x^2 + 6 = 8x 
x^2-4x+3=0 
(x - 1)(x - 3) 
x=1 or 3 y=2 or 2/3 

so 4x^2+9y^2 = 4+36 = 40 answer
1 5 1
how complicated!!
But anyways its correct
Comment has been deleted
what is stupid?
2015-06-27T21:20:35+05:30
We have to find 4x²+9y² not 4x+9y.
2x+3y=8;xy=2.
(2x+3y)^{2} =   8^{2}
(2x) ^{2} +2*2x*3y+(3y) ^{2} =64
4x^{2} +12xy+9y^{2}=64
4x^{2}+9y ^{2} =64-12xy
⇒Substituting xy as 2 we get
4 x^{2} +9 y^{2} =64-12*2=64-24=40.
Ans:4x+9y=40.
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