Math Problem Statement

Use a computer algebra system to graph the function f(x) = (1/12)x * sqrt(12 - x) and determine all absolute extrema on the closed interval [0, 12].

Solution

The problem asks to graph the function f(x)=112x12xf(x) = \frac{1}{12} x \sqrt{12 - x} and determine the absolute extrema on the closed interval [0,12][0, 12].

Step-by-Step Solution:

  1. Domain of the function:
    Since 12x\sqrt{12 - x} is defined only when 12x012 - x \geq 0, we have x12x \leq 12. The domain is [0,12][0, 12].

  2. Critical Points:
    To find the critical points, we first need the derivative of the function f(x)f(x). Using the product rule and chain rule: f(x)=112x12xf(x) = \frac{1}{12} x \sqrt{12 - x} Let’s differentiate this:

    f(x)=112(12x+x1212x)f'(x) = \frac{1}{12} \left( \sqrt{12 - x} + x \cdot \frac{-1}{2\sqrt{12 - x}} \right) Simplifying this: f(x)=112(12xx212x)f'(x) = \frac{1}{12} \left( \sqrt{12 - x} - \frac{x}{2\sqrt{12 - x}} \right) To find critical points, set f(x)=0f'(x) = 0: 12xx212x=0\sqrt{12 - x} - \frac{x}{2\sqrt{12 - x}} = 0 Multiply through by 212x2\sqrt{12 - x} to eliminate the denominator: 2(12x)x=02(12 - x) - x = 0 Simplifying: 242xx=024=3xx=824 - 2x - x = 0 \quad \Rightarrow \quad 24 = 3x \quad \Rightarrow \quad x = 8 So, x=8x = 8 is a critical point.

  3. Endpoints:
    We need to evaluate f(x)f(x) at the endpoints x=0x = 0 and x=12x = 12, as well as at the critical point x=8x = 8.

    • f(0)=1120120=0f(0) = \frac{1}{12} \cdot 0 \cdot \sqrt{12 - 0} = 0
    • f(12)=112121212=0f(12) = \frac{1}{12} \cdot 12 \cdot \sqrt{12 - 12} = 0
    • f(8)=1128128=8124=8122=1612=43f(8) = \frac{1}{12} \cdot 8 \cdot \sqrt{12 - 8} = \frac{8}{12} \cdot \sqrt{4} = \frac{8}{12} \cdot 2 = \frac{16}{12} = \frac{4}{3}
  4. Conclusion (Extrema):

    • At x=0x = 0, f(0)=0f(0) = 0
    • At x=8x = 8, f(8)=43f(8) = \frac{4}{3} (maximum)
    • At x=12x = 12, f(12)=0f(12) = 0

    Therefore, the absolute maximum occurs at x=8x = 8, and the absolute minimum occurs at both x=0x = 0 and x=12x = 12.

Would you like me to show a graph of the function or explain any step in more detail?

Related Questions:

  1. How do you apply the product rule and chain rule in this example?
  2. Can the function have any other critical points in the interval?
  3. What would happen if we extended the interval beyond [0,12][0, 12]?
  4. How would the second derivative help in confirming the nature of the critical points?
  5. Could there be another approach to finding the absolute extrema without derivatives?

Tip: Always check endpoints when determining absolute extrema on a closed interval!

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Math Problem Analysis

Mathematical Concepts

Calculus
Critical Points
Extrema
Derivatives

Formulas

f(x) = (1/12) * x * sqrt(12 - x)
f'(x) = (1/12) * (sqrt(12 - x) - (x/2) / sqrt(12 - x))

Theorems

Product Rule
Chain Rule
Critical Points Theorem

Suitable Grade Level

Grades 11-12