Hi. I have the equation x^2 + 4y^2, with the constraint xy=1. (with m being used to indicate theta)

Hence, F(x,y,m)= x^2 + 4y^2 + m(xy-1).

Derivatives:

Fx= 2x + my=0

Fy= 8y+ mx=0

Fm= xy-1=0.

What is the correct way to solve for y and x; I keep getting y= the sq. root of 1/2, but the book says this is wrong.

Many thanks

Jay