- #1
GWR309
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f(x,y)=x^2y with the constraint of x^2+2y^2=6
Use lagrange multipliers to find the extrema.
Thanks!
Use lagrange multipliers to find the extrema.
Thanks!
Prove It said:Well, have you tried to solve the system
\(\displaystyle \displaystyle \begin{align*} \nabla f(x, y) &= \lambda \nabla g(x, y) \\ g(x, y) &= k \end{align*}\)
yet? Here \(\displaystyle \displaystyle f(x, y) = x^2y\) and \(\displaystyle \displaystyle g(x, y) = x^2 + 2y^2 = 6\).
GWR309 said:f(x,y)=x^2y with the constraint of x^2+2y^2=6
Use lagrange multipliers to find the extrema.
Thanks!
GWR309 said:Yeah I tried. I ended up with 2y^2+sqrt(2)y-6 which doesn't seem right and if it is right, I don't know how to solve it
MarkFL said:The way I learned to use Lagrange multipliers, while Prove It is being more rigorous, is to write:
The objective function is:
\(\displaystyle f(x,y)=x^2y\)
subject to the constraint:
\(\displaystyle g(x,y)=x^2+2y^2-6=0\)
Now, first find the implications of the system:
\(\displaystyle f_x(x,y)=\lambda g_x(x,y)\)
\(\displaystyle f_y(x,y)=\lambda g_y(x,y)\)
Then use the implications in the constraint to find the critical points. Can you write down the system from which to take the implications?
Lagrange multipliers are a mathematical tool used to find the extrema (maximum or minimum) of a function subject to one or more constraints.
To use Lagrange multipliers, we first set up an equation involving the function we want to optimize (in this case, f(x,y)=x^2y) and the constraints. We then use the method of partial derivatives to solve for the values of x and y that will give us the extrema.
Lagrange multipliers are useful because they allow us to find the extrema of a function subject to constraints without having to solve a system of equations.
Yes, Lagrange multipliers can be used with any number of variables. However, as the number of variables increases, the equations become more complex and may be more difficult to solve.
Lagrange multipliers are commonly used in economics, physics, and engineering to optimize functions subject to constraints. For example, they can be used to determine the most efficient way to allocate resources or to design structures that can withstand certain forces.