8. The function f(x, y) = x² + 4y² - 8x + 16y - 2 has one critical point. Determine its location and type.

Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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**Problem 8: Identifying the Critical Point of a Multivariable Function**

The task is to analyze the function \( f(x, y) = x^2 + 4y^2 - 8x + 16y - 2 \) and determine the location and type of its critical point.

To find the critical point, we'll take partial derivatives of the function with respect to \( x \) and \( y \).

1. **Partial Derivative with respect to \( x \):**
   - \( \frac{\partial f}{\partial x} = 2x - 8 \)

2. **Partial Derivative with respect to \( y \):**
   - \( \frac{\partial f}{\partial y} = 8y + 16 \)

Set both partial derivatives to zero to find critical points:

- \( 2x - 8 = 0 \)
  - Solving for \( x \) gives \( x = 4 \).

- \( 8y + 16 = 0 \)
  - Solving for \( y \) gives \( y = -2 \).

Thus, the critical point is \((4, -2)\).

To determine the type of critical point, we consider the Hessian matrix:

\[ H = \begin{bmatrix}
\frac{\partial^2 f}{\partial x^2} & \frac{\partial^2 f}{\partial x \partial y}\\
\frac{\partial^2 f}{\partial y \partial x} & \frac{\partial^2 f}{\partial y^2}
\end{bmatrix} \]

Where:
- \( \frac{\partial^2 f}{\partial x^2} = 2 \)
- \( \frac{\partial^2 f}{\partial y^2} = 8 \)
- \( \frac{\partial^2 f}{\partial x \partial y} = 0 \)

The Hessian determinant \( D = (2)(8) - (0)^2 = 16 \) which is positive, and since \( \frac{\partial^2 f}{\partial x^2} = 2 \) is positive, the critical point is a local minimum.

**Conclusion:**
The function \( f(x, y) = x^2 + 4y^2 - 8x + 16y - 2 \) has
Transcribed Image Text:**Problem 8: Identifying the Critical Point of a Multivariable Function** The task is to analyze the function \( f(x, y) = x^2 + 4y^2 - 8x + 16y - 2 \) and determine the location and type of its critical point. To find the critical point, we'll take partial derivatives of the function with respect to \( x \) and \( y \). 1. **Partial Derivative with respect to \( x \):** - \( \frac{\partial f}{\partial x} = 2x - 8 \) 2. **Partial Derivative with respect to \( y \):** - \( \frac{\partial f}{\partial y} = 8y + 16 \) Set both partial derivatives to zero to find critical points: - \( 2x - 8 = 0 \) - Solving for \( x \) gives \( x = 4 \). - \( 8y + 16 = 0 \) - Solving for \( y \) gives \( y = -2 \). Thus, the critical point is \((4, -2)\). To determine the type of critical point, we consider the Hessian matrix: \[ H = \begin{bmatrix} \frac{\partial^2 f}{\partial x^2} & \frac{\partial^2 f}{\partial x \partial y}\\ \frac{\partial^2 f}{\partial y \partial x} & \frac{\partial^2 f}{\partial y^2} \end{bmatrix} \] Where: - \( \frac{\partial^2 f}{\partial x^2} = 2 \) - \( \frac{\partial^2 f}{\partial y^2} = 8 \) - \( \frac{\partial^2 f}{\partial x \partial y} = 0 \) The Hessian determinant \( D = (2)(8) - (0)^2 = 16 \) which is positive, and since \( \frac{\partial^2 f}{\partial x^2} = 2 \) is positive, the critical point is a local minimum. **Conclusion:** The function \( f(x, y) = x^2 + 4y^2 - 8x + 16y - 2 \) has
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We have to find critical point and its location

Topic:- Application of derivative.

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