Math Problem Statement

Determine the exact values at which inflection points occur, if any, of the function f(x) = x / e^(8x).

Solution

To determine the exact values of inflection points for the function f(x)=xe8xf(x) = \frac{x}{e^{8x}}, we need to find where the second derivative changes sign. Let's go through the steps:

Step 1: First Derivative

The function is: f(x)=xe8xf(x) = \frac{x}{e^{8x}} Using the quotient rule, where u=xu = x and v=e8xv = e^{8x}: f(x)=vuuvv2=e8x1x8e8x(e8x)2f'(x) = \frac{v \cdot u' - u \cdot v'}{v^2} = \frac{e^{8x} \cdot 1 - x \cdot 8e^{8x}}{(e^{8x})^2} Simplifying this: f(x)=e8x8xe8xe16x=e8x(18x)e16x=18xe8xf'(x) = \frac{e^{8x} - 8x \cdot e^{8x}}{e^{16x}} = \frac{e^{8x}(1 - 8x)}{e^{16x}} = \frac{1 - 8x}{e^{8x}}

Step 2: Second Derivative

Now, take the derivative of f(x)=18xe8xf'(x) = \frac{1 - 8x}{e^{8x}} to find f(x)f''(x).

Using the quotient rule again: f(x)=e8x(8)(18x)8e8x(e8x)2f''(x) = \frac{e^{8x} \cdot (-8) - (1 - 8x) \cdot 8e^{8x}}{(e^{8x})^2} Simplify this expression: f(x)=8e8x8(18x)e8xe16x=8e8x(1+18x)e16x=8(28x)e8xf''(x) = \frac{-8e^{8x} - 8(1 - 8x)e^{8x}}{e^{16x}} = \frac{-8e^{8x}(1 + 1 - 8x)}{e^{16x}} = \frac{-8(2 - 8x)}{e^{8x}}

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Math Problem Analysis

Mathematical Concepts

Calculus
Inflection Points
Derivatives

Formulas

Quotient rule for derivatives
Second derivative for inflection points

Theorems

Inflection point theorem (change of concavity)

Suitable Grade Level

College-level Calculus