Math Problem Statement

find the minimum value for the function f(x) = x^x

Solution

To find the minimum value of the function f(x)=xxf(x) = x^x, we can proceed by first rewriting it in a form that simplifies differentiation, allowing us to locate any critical points.

Step 1: Rewrite the Function Using Logarithms

Rewrite f(x)=xxf(x) = x^x in a way that allows differentiation: f(x)=exlnxf(x) = e^{x \ln x} Let g(x)=xlnxg(x) = x \ln x, so that f(x)=eg(x)f(x) = e^{g(x)}. The minimum of f(x)f(x) will occur where g(x)g(x) reaches its minimum, since exe^x is an increasing function.

Step 2: Find the Derivative of g(x)g(x)

To find the critical points of g(x)=xlnxg(x) = x \ln x, we take its derivative: g(x)=lnx+1g'(x) = \ln x + 1 Set g(x)=0g'(x) = 0 to find critical points: lnx+1=0lnx=1x=e1=1e\ln x + 1 = 0 \Rightarrow \ln x = -1 \Rightarrow x = e^{-1} = \frac{1}{e}

Step 3: Determine the Nature of the Critical Point

To confirm that x=1ex = \frac{1}{e} gives a minimum, consider the second derivative of g(x)g(x): g(x)=1xg''(x) = \frac{1}{x} Since g(x)>0g''(x) > 0 for x>0x > 0, the function g(x)g(x) is concave up at x=1ex = \frac{1}{e}, indicating a minimum at this point.

Step 4: Calculate the Minimum Value

Now, evaluate f(x)f(x) at x=1ex = \frac{1}{e}: f(1e)=(1e)1e=e1ef\left( \frac{1}{e} \right) = \left( \frac{1}{e} \right)^{\frac{1}{e}} = e^{-\frac{1}{e}}

Thus, the minimum value of f(x)=xxf(x) = x^x is: e1e0.6922\boxed{e^{-\frac{1}{e}} \approx 0.6922}

Would you like more details or have any questions?

Here are five related questions:

  1. How can you find maximum points for similar functions?
  2. What happens to f(x)=xxf(x) = x^x as xx \to \infty and x0+x \to 0^+?
  3. Can the minimum be obtained without calculus?
  4. How does the derivative g(x)=lnx+1g'(x) = \ln x + 1 behave near x=1x = 1?
  5. Are there any other local extrema for f(x)=xxf(x) = x^x?

Tip: Rewriting a function in terms of ee can simplify differentiation and reveal critical points easily.

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Math Problem Analysis

Mathematical Concepts

Calculus
Exponential Functions
Logarithmic Differentiation

Formulas

f(x) = e^{x ln(x)}
g(x) = x ln(x)
g'(x) = ln(x) + 1
g''(x) = 1/x

Theorems

First Derivative Test for Critical Points
Second Derivative Test for Concavity

Suitable Grade Level

Grades 11-12