Math Problem Statement

Solution

The problem presented is to find the number of real values of xx where xx is a real number that satisfies the given equation:

logxx=32xlog3\log x^x = 3 - 2x \log 3

To solve this, follow these steps:

  1. Simplify the equation: logxx=xlogx\log x^x = x \log x Thus, the equation becomes: xlogx=32xlog3x \log x = 3 - 2x \log 3

  2. Isolate logx\log x: xlogx+2xlog3=3x \log x + 2x \log 3 = 3 Factor out xx from the left side: x(logx+2log3)=3x (\log x + 2 \log 3) = 3 Simplify further: x(logx+log9)=3x (\log x + \log 9) = 3 xlog(9x)=3x \log (9x) = 3

  3. Analyze the function f(x)=xlog(9x)f(x) = x \log (9x): Define f(x)=xlog(9x)f(x) = x \log (9x). We need to find the values of xx for which f(x)=3f(x) = 3.

  4. Find the domain: Since xlog(9x)x \log (9x) involves a logarithm, 9x9x must be positive: 9x>0    x>09x > 0 \implies x > 0

  5. Behavior of the function:

    • As xx approaches 0+0^+, f(x)f(x) approaches 00.
    • As xx increases, we need to check if f(x)f(x) can reach 3.
  6. First derivative test: Take the derivative of f(x)f(x) to understand its behavior: f(x)=xlog(9x)f(x) = x \log (9x) Use the product rule: f(x)=log(9x)+x19x9=log(9x)+1f'(x) = \log (9x) + x \cdot \frac{1}{9x} \cdot 9 = \log (9x) + 1 f(x)=log(9x)+1f'(x) = \log (9x) + 1 For f(x)=0f'(x) = 0: log(9x)+1=0\log (9x) + 1 = 0 log(9x)=1\log (9x) = -1 9x=1019x = 10^{-1} x=19x = \frac{1}{9}

    f(x)f(x) is increasing for x>19x > \frac{1}{9} because f(x)>0f'(x) > 0.

  7. Conclusion: Since f(x)f(x) is strictly increasing for x>19x > \frac{1}{9}, and f(x)0f(x) \to 0 as x0+x \to 0^+, there is exactly one real solution for xx such that f(x)=3f(x) = 3.

Thus, there is exactly one real value of xx that satisfies the given equation.

Do you want more details or have any questions?


Here are 8 related questions:

  1. What is the range of the function f(x)=xlog(9x)f(x) = x \log (9x) for x>0x > 0?
  2. How does the function f(x)=xlog(9x)f(x) = x \log (9x) behave as xx approaches infinity?
  3. Can f(x)=xlog(9x)f(x) = x \log (9x) have any complex solutions?
  4. How would the equation change if the logarithm had a different base, such as log2\log_2?
  5. What happens to the solution if the constant term on the right side is different, for example, 44 instead of 33?
  6. How can the derivative test be used to find local minima and maxima of f(x)f(x)?
  7. What are the properties of the logarithm function that are useful in solving equations like this one?
  8. How can numerical methods be used to approximate solutions to transcendental equations?

Tip: Always remember to check the domain of the logarithmic function to ensure all arguments are positive and valid.

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Math Problem Analysis

Mathematical Concepts

Logarithms
Exponential Functions
Derivatives

Formulas

Logarithm properties
Product rule for derivatives

Theorems

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Suitable Grade Level

Advanced High School