Math Problem Statement

Find the absolute maximum value and the absolute minimum value, if any, of the function. (If an answer does not exist, enter DNE.)

f(x) = 

1

2

x4 − 

2

3

x3 − 2x2 + 3 on [−3, 3]

maximum minimum 

Solution

To find the absolute maximum and minimum values of the given function f(x)=12x423x32x2+3f(x) = \frac{1}{2}x^4 - \frac{2}{3}x^3 - 2x^2 + 3 on the interval [3,3][-3, 3], follow these steps:


Step 1: Take the derivative of f(x)f(x)

To find critical points, calculate the derivative f(x)f'(x): f(x)=2x32x24xf'(x) = 2x^3 - 2x^2 - 4x


Step 2: Factorize f(x)f'(x)

Factorize f(x)f'(x) to find critical points: f(x)=2x(x2x2)f'(x) = 2x(x^2 - x - 2)

Factorize x2x2x^2 - x - 2: f(x)=2x(x2)(x+1)f'(x) = 2x(x - 2)(x + 1)


Step 3: Solve f(x)=0f'(x) = 0

Set f(x)=0f'(x) = 0: 2x(x2)(x+1)=02x(x - 2)(x + 1) = 0 The critical points are: x=0,x=2,x=1x = 0, \, x = 2, \, x = -1


Step 4: Evaluate f(x)f(x) at critical points and endpoints

Evaluate f(x)f(x) at x=3,1,0,2,3x = -3, -1, 0, 2, 3.

  • At x=3x = -3: f(3)=12(3)423(3)32(3)2+3=40.5+1818+3=43.5f(-3) = \frac{1}{2}(-3)^4 - \frac{2}{3}(-3)^3 - 2(-3)^2 + 3 = 40.5 + 18 - 18 + 3 = 43.5

  • At x=1x = -1: f(1)=12(1)423(1)32(1)2+3=0.5+232+31.167f(-1) = \frac{1}{2}(-1)^4 - \frac{2}{3}(-1)^3 - 2(-1)^2 + 3 = 0.5 + \frac{2}{3} - 2 + 3 \approx 1.167

  • At x=0x = 0: f(0)=12(0)423(0)32(0)2+3=3f(0) = \frac{1}{2}(0)^4 - \frac{2}{3}(0)^3 - 2(0)^2 + 3 = 3

  • At x=2x = 2: f(2)=12(2)423(2)32(2)2+3=81638+32.333f(2) = \frac{1}{2}(2)^4 - \frac{2}{3}(2)^3 - 2(2)^2 + 3 = 8 - \frac{16}{3} - 8 + 3 \approx -2.333

  • At x=3x = 3: f(3)=12(3)423(3)32(3)2+3=40.51818+3=7.5f(3) = \frac{1}{2}(3)^4 - \frac{2}{3}(3)^3 - 2(3)^2 + 3 = 40.5 - 18 - 18 + 3 = 7.5


Step 5: Identify the absolute maximum and minimum

  • Absolute maximum: f(3)=43.5f(-3) = 43.5
  • Absolute minimum: f(2)2.333f(2) \approx -2.333

Final Answer:

  • Maximum: 43.543.5 at x=3x = -3
  • Minimum: 2.333-2.333 at x=2x = 2

Would you like a detailed explanation of any specific step? Here are related questions:

  1. How is the derivative of a function calculated?
  2. Why do we check endpoints in addition to critical points?
  3. How do you factorize a cubic polynomial?
  4. What is the difference between local and absolute extrema?
  5. How can you confirm extrema using the second derivative test?

Tip: Always evaluate endpoints in a closed interval to ensure all potential extrema are considered.

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Math Problem Analysis

Mathematical Concepts

Calculus
Critical Points
Absolute Extrema
Polynomial Functions

Formulas

Derivative of f(x): f'(x) = nx^(n-1)
Critical points: Solve f'(x) = 0
Evaluate f(x) at critical points and endpoints

Theorems

Extreme Value Theorem

Suitable Grade Level

Grades 11-12 or College Calculus I