Max/Min using Lagrange Multipliers: F(x,y) = x^2 + y^2 ; xy = 1

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SUMMARY

The discussion focuses on finding the maximum and minimum values of the function F(x,y) = x^2 + y^2 subject to the constraint xy = 1 using Lagrange Multipliers. The equations derived from the method include 2x = L*y, 2y = L*x, and the constraint xy = 1. The user expresses confusion about how to derive x = L^2/4 and y = L^2/4 from the equations x = L*y/2 and y = L*x/2. The solution requires further manipulation of these equations to isolate L and express x and y in terms of L.

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Homework Statement



Find max/min using L.M of the function :

F(x,y) = x^2 + y^2 ; xy = 1

let G(x,y) = xy - 1

F_x = 2x
F_y = 2y
G_x = y
G_y = x

F_x = L*G_x
F_y = L*G_y
G(x,y) = 1


1) 2x = L * y
2) 2y = L * x
3 ) xy = 1

Now I need to solve those equations.

so x = LY/2 ; y = LX/2

Then if I plug it in I get X = L^2/4 and similar for Y
Not sure how to approach that step
 
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x=Ly/2 and y=Lx/2 doesn't tell you x=L^2/4. Try that again.
 

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