How do I solve a Lagrange Multiplier problem with a given constraint?

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Discussion Overview

The discussion revolves around solving Lagrange Multiplier problems with specific constraints, focusing on the mathematical techniques involved in applying the method to find extrema of functions subject to constraints. Participants share their approaches and seek clarification on the steps involved.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Exploratory

Main Points Raised

  • One participant presents a function f(x,y) = x² - y² with the constraint x² + y² = 1 and expresses uncertainty about the next steps after finding partial derivatives.
  • Another participant questions whether the constraint should be adjusted from equal to 1 to equal to 0, indicating a potential misunderstanding of the formulation.
  • A participant attempts to derive the Lagrange multiplier by setting up the equation 2x + (lag. symbol)2x = 0, leading to a proposed value for the Lagrange multiplier of -1.
  • There is a suggestion to substitute values into the original function to find critical points, with proposed points being (+-1,0), (0,+-1), or (0,0), though the correctness of this approach is uncertain.
  • Another participant introduces a new problem involving F(x,y) = x²y and G(x,y) = x² + 2y² = 6, calculating partial derivatives and questioning the validity of their derived Lagrange multiplier as y.
  • A participant outlines three equations derived from the problem, including partial derivatives and the constraint, and expresses the goal of finding numbers that satisfy all equations.

Areas of Agreement / Disagreement

The discussion contains multiple competing views and approaches to solving Lagrange Multiplier problems. Participants express uncertainty and seek clarification on various steps, indicating that no consensus has been reached on the methods or solutions presented.

Contextual Notes

Participants have not fully resolved the implications of their assumptions regarding the constraints, nor have they clarified the conditions under which their derived values hold true. There are also unresolved mathematical steps in the derivations presented.

Arden1528
We have started to do Lagrange Multi. in my class and my book has a very short section on how to solve these. I was wondering if someone couls help.
The problem is f(x,y)=x^2-y^2 with the constraint x^2+y^2=1.
I have found the partial derv. but I am not sure on what else to do. Any help would be sweet, later.
 
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In my problem I have the constraint equal to 1, should I adjust it and have it equal to 0?
 
So then for my problem I would get something like

the partial of X: 2X+(lag. symbol)2X=0
thus getting (Lag. Symbol)= -1
 
Then take that 1 and 0 and plug them into the orig. equation of F(X)
and get (+-1,0) or (0,+-1) or (0,0). Then I have the conditions to make this either a max or min. Value. Is this correct?
 
Alright, then for my next problem I have
F(X);x^2y and G(X);x^2+2y^2=6

The partials of x I get
2xy+(Lang.)2x=0, giving me (Lang.)=y, can this be true?
 
I have thought about the three equations
Partial x
2xy=(Lang.)2x
Partial y
x^2=(Lang.)4y
and
x^2+2y^2=6
and am looking for numbers that satisfy all equations. So I would get something like...
 

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