Math Problem Statement

Find the absolute maximum and minimum values of

f(x, y) = e −x 2−y 2 (x 2 + 2y 2 ) on the disk x 2 + y 2 ≤ 4

Solution

To find the absolute maximum and minimum values of the function

f(x,y)=ex2y2(x2+2y2)f(x, y) = e^{-x^2 - y^2}(x^2 + 2y^2)

on the disk x2+y24x^2 + y^2 \leq 4, we need to consider two cases: the interior of the disk and the boundary.

Step 1: Finding Critical Points in the Interior

First, let’s find the critical points of f(x,y)f(x, y) by setting the partial derivatives with respect to xx and yy equal to zero.

  1. Partial derivative with respect to xx: fx=x(ex2y2(x2+2y2))f_x = \frac{\partial}{\partial x}\left(e^{-x^2 - y^2}(x^2 + 2y^2)\right)

    Using the product rule: fx=ex2y2(2x)ex2y2(2x)(x2+2y2)=0f_x = e^{-x^2 - y^2}(2x) - e^{-x^2 - y^2}(2x)(x^2 + 2y^2) = 0

This

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Math Problem Analysis

Mathematical Concepts

Multivariable Calculus
Optimization
Critical Points
Partial Derivatives

Formulas

f(x, y) = e^(-x^2 - y^2)(x^2 + 2y^2)
Critical point condition: ∂f/∂x = 0, ∂f/∂y = 0

Theorems

Extreme Value Theorem
Optimization on a Closed Region

Suitable Grade Level

College/University Level (Calculus II/III)