Given f(x,y)= x³(x²y³-2y²), find all of the first and second partial derivatives.

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 Statement:**

Given the function \( f(x,y) = x^3 (x^2 y^3 - 2y^2) \), find all of the first and second partial derivatives.

**Solution:**

We start by finding the first partial derivatives of the function \( f \) with respect to \( x \) and \( y \).

**Finding the First Partial Derivative with respect to \( x \) (\( f_x \)):**

Given:
\[ f(x,y) = x^3 (x^2 y^3 - 2y^2) \]

Let's expand the expression first:
\[ f(x,y) = x^5 y^3 - 2 x^3 y^2 \]

Now, take the partial derivative with respect to \( x \):
\[ f_x = \frac{\partial}{\partial x} (x^5 y^3 - 2 x^3 y^2) \]
\[ f_x = 5 x^4 y^3 - 6 x^2 y^2 \]

**Finding the First Partial Derivative with respect to \( y \) (\( f_y \)):**

Again, take the partial derivative with respect to \( y \):
\[ f_y = \frac{\partial}{\partial y} (x^5 y^3 - 2 x^3 y^2) \]
\[ f_y = 3 x^5 y^2 - 4 x^3 y \]

Next, we find the second partial derivatives. We need \( f_{xx}, f_{xy}, f_{yx}, f_{yy} \).

**Finding the Second Partial Derivative with respect to \( x \) (\( f_{xx} \)):**
\[ f_{xx} = \frac{\partial}{\partial x} (5 x^4 y^3 - 6 x^2 y^2) \]
\[ f_{xx} = 20 x^3 y^3 - 12 x y^2 \]

**Finding the Second Partial Derivative with respect to \( y \) (\( f_{yy} \)):**
\[ f_{yy} = \frac{\partial}{\partial y} (3 x^5 y^2 - 4 x^3 y) \]
\[ f_{yy} = 6 x^5 y - 4 x^3 \]

**Finding the Mixed Partial Derivative
Transcribed Image Text:**Problem Statement:** Given the function \( f(x,y) = x^3 (x^2 y^3 - 2y^2) \), find all of the first and second partial derivatives. **Solution:** We start by finding the first partial derivatives of the function \( f \) with respect to \( x \) and \( y \). **Finding the First Partial Derivative with respect to \( x \) (\( f_x \)):** Given: \[ f(x,y) = x^3 (x^2 y^3 - 2y^2) \] Let's expand the expression first: \[ f(x,y) = x^5 y^3 - 2 x^3 y^2 \] Now, take the partial derivative with respect to \( x \): \[ f_x = \frac{\partial}{\partial x} (x^5 y^3 - 2 x^3 y^2) \] \[ f_x = 5 x^4 y^3 - 6 x^2 y^2 \] **Finding the First Partial Derivative with respect to \( y \) (\( f_y \)):** Again, take the partial derivative with respect to \( y \): \[ f_y = \frac{\partial}{\partial y} (x^5 y^3 - 2 x^3 y^2) \] \[ f_y = 3 x^5 y^2 - 4 x^3 y \] Next, we find the second partial derivatives. We need \( f_{xx}, f_{xy}, f_{yx}, f_{yy} \). **Finding the Second Partial Derivative with respect to \( x \) (\( f_{xx} \)):** \[ f_{xx} = \frac{\partial}{\partial x} (5 x^4 y^3 - 6 x^2 y^2) \] \[ f_{xx} = 20 x^3 y^3 - 12 x y^2 \] **Finding the Second Partial Derivative with respect to \( y \) (\( f_{yy} \)):** \[ f_{yy} = \frac{\partial}{\partial y} (3 x^5 y^2 - 4 x^3 y) \] \[ f_{yy} = 6 x^5 y - 4 x^3 \] **Finding the Mixed Partial Derivative
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