Math Problem Statement

f(x) = 4x(1-x^2), x = [0,1]. what is the mean

Solution

To find the mean of the function f(x)=4x(1x2)f(x) = 4x(1 - x^2) over the interval [0,1][0, 1], we use the formula for the mean value of a function on a closed interval:

Mean=1baabf(x)dx\text{Mean} = \frac{1}{b-a} \int_{a}^{b} f(x) \, dx

where a=0a = 0 and b=1b = 1. Thus, the mean becomes:

Mean=014x(1x2)dx\text{Mean} = \int_{0}^{1} 4x(1 - x^2) \, dx

Step 1: Expand the integrand

First, expand 4x(1x2)4x(1 - x^2):

4x(1x2)=4x4x34x(1 - x^2) = 4x - 4x^3

Step 2: Integrate term-by-term

Now, integrate each term separately:

01(4x4x3)dx=014xdx014x3dx\int_{0}^{1} (4x - 4x^3) \, dx = \int_{0}^{1} 4x \, dx - \int_{0}^{1} 4x^3 \, dx

Calculate these integrals:

  1. 014xdx=4[x22]01=412=2\int_{0}^{1} 4x \, dx = 4 \left[ \frac{x^2}{2} \right]_{0}^{1} = 4 \cdot \frac{1}{2} = 2

  2. 014x3dx=4[x44]01=414=1\int_{0}^{1} 4x^3 \, dx = 4 \left[ \frac{x^4}{4} \right]_{0}^{1} = 4 \cdot \frac{1}{4} = 1

Step 3: Subtract the results

The integral from 0 to 1 of 4x(1x2)4x(1 - x^2) is:

21=12 - 1 = 1

Step 4: Divide by the length of the interval

The length of the interval [0,1][0,1] is 11, so the mean is:

Mean=111=1\text{Mean} = \frac{1}{1} \cdot 1 = 1

Therefore, the mean value of the function f(x)=4x(1x2)f(x) = 4x(1 - x^2) over the interval [0,1][0,1] is 11.

Would you like more details or have any questions?

Here are some related questions:

  1. How would you find the mean for a different interval, such as [0,2][0,2]?
  2. What would the mean be if the function was f(x)=4x2(1x2)f(x) = 4x^2(1 - x^2)?
  3. Can you find the average rate of change of f(x)f(x) over [0,1][0,1]?
  4. What is the maximum value of f(x)f(x) in the interval [0,1][0,1]?
  5. How would you find the median value of f(x)f(x) over the interval?

Tip: When integrating polynomial functions, break them down into simpler terms and integrate term-by-term for ease.

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Math Problem Analysis

Mathematical Concepts

Calculus
Integration
Mean of a Function

Formulas

Mean value of a function: (1 / (b - a)) ∫[a,b] f(x) dx
Integral of polynomial functions

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12