Created on 2024-06-20Asked by Samuel Johnson (Solvelet student)
Use the method of Lagrange multipliers to find the maximum value of f(x,y)=xy subject to the constraint x2+y2=1.
Solution
To find the maximum value of f(x,y)=xy subject to the constraint x2+y2=1 using the method of Lagrange multipliers, follow these steps: 1. Define the Lagrangian function: L(x,y,λ)=xy+λ(1−x2−y2). 2. Take the partial derivatives and set them to zero: ∂x∂L=y−2λx=0,∂y∂L=x−2λy=0,∂λ∂L=1−x2−y2=0. 3. Solve the system of equations: y=2λx⟹x=2λy. Substitute into x2+y2=1: (2λy)2+y2=1⟹4λ2y2+y2=1⟹y2(4λ2+1)=1.y=±4λ2+11⟹x=±4λ2+12λ. 4. Find λ by substituting x and y: 4λ2+12λ=2λ⋅±4λ2+11⟹λ=±21. 5. Evaluate f(x,y): x=2±1,y=2±1⟹f(x,y)=(21)(21)=21. Therefore, the maximum value of f(x,y) is 21. Solved on Solvelet with Basic AI Model
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DefinitionMathematical methods that seeks to find the best result to a problem by minimizing or maximizing a function Methods include calculus-based methods (e.g. Lagrange multipliers), linear programming and heuristic methods (e.g. genetic algorithms). Case study : Use of Lagrange multipliers for finding extrema for f(x,y)=xy under the constraint x2+y2=1.