Math Problem Statement

Find the absolute maximum value over [0, 6].

f(x)=2x^2-2x-2

Solution

To find the absolute maximum value of the function f(x)=2x22x2f(x) = 2x^2 - 2x - 2 on the interval [0,6][0, 6], follow these steps:

Step 1: Compute the derivative

The first step is to find the critical points by taking the derivative of f(x)f(x): f(x)=ddx(2x22x2)=4x2f'(x) = \frac{d}{dx}(2x^2 - 2x - 2) = 4x - 2

Step 2: Find critical points

Set f(x)=0f'(x) = 0 to solve for xx: 4x2=0    x=24=12.4x - 2 = 0 \quad \implies \quad x = \frac{2}{4} = \frac{1}{2}.

Step 3: Evaluate f(x)f(x) at the critical point and endpoints

We need to evaluate f(x)f(x) at x=0x = 0, x=6x = 6, and x=12x = \frac{1}{2}.

  1. At x=0x = 0: f(0)=2(0)22(0)2=2f(0) = 2(0)^2 - 2(0) - 2 = -2

  2. At x=12x = \frac{1}{2}: f(12)=2(12)22(12)2f\left(\frac{1}{2}\right) = 2\left(\frac{1}{2}\right)^2 - 2\left(\frac{1}{2}\right) - 2 f(12)=2(14)12=1212=52=2.5f\left(\frac{1}{2}\right) = 2\left(\frac{1}{4}\right) - 1 - 2 = \frac{1}{2} - 1 - 2 = -\frac{5}{2} = -2.5

  3. At x=6x = 6: f(6)=2(6)22(6)2=2(36)122=7214=58f(6) = 2(6)^2 - 2(6) - 2 = 2(36) - 12 - 2 = 72 - 14 = 58

Step 4: Determine the absolute maximum

The values of f(x)f(x) are:

  • f(0)=2f(0) = -2
  • f(12)=2.5f\left(\frac{1}{2}\right) = -2.5
  • f(6)=58f(6) = 58

The absolute maximum value of f(x)f(x) on [0,6][0, 6] is: 58 at x=6.\boxed{58 \text{ at } x = 6.}


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5 Related Questions:

  1. How do you determine the absolute minimum value on a closed interval?
  2. What happens if there are no critical points inside the interval?
  3. How do you verify if a critical point is a maximum or minimum?
  4. How do absolute extrema differ from relative extrema?
  5. Can you explain why the endpoints of the interval are always checked?

Tip:

Always check the function's value at both the critical points and the endpoints when finding absolute extrema on a closed interval.

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Math Problem Analysis

Mathematical Concepts

Calculus
Critical Points
Absolute Maximum and Minimum
Evaluating Functions on a Closed Interval

Formulas

Derivative: f'(x) = 4x - 2
Function evaluation: f(x) = 2x^2 - 2x - 2

Theorems

Extreme Value Theorem: A continuous function on a closed interval attains its maximum and minimum values.

Suitable Grade Level

Grades 11-12 or College Level (Calculus I)