Proving x^x=4: A Brain Teaser with Multiple Solutions | Homework Help

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In summary, the conversation discusses the equation x^x=4 and the possibility of there being more than one solution. However, it is concluded that the only solution is x=2 and this can be proved using logarithmic differentiation or the Newton-raphson method.
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ssb
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Homework Statement


[tex]x^x=4[/tex]

this is a brain teaser a co-worker gave me. I can take the ln of bothb sides... etc but it ends up going in a circle. any guidance on this problem? I know one solution is 2 but he said there is at least one more solution.
 
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  • #2
ssb said:
I know one solution is 2 but he said there is at least one more solution.
He's incorrect; the only solution to the equation is x=2. I can't think of an elegant proof right now, but you could use the Newton-raphson method and observe that no matter your choice for intial solution, the algorithm will always converge to 2.
 
  • #3
Using logarithmic differentiation, you can show that the function has only a single critical point (a minimum) at x = 1/e. By observation, x = 2 is a solution. Since there are no other critical points, this must be the only solution.
 
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FAQ: Proving x^x=4: A Brain Teaser with Multiple Solutions | Homework Help

What is the problem with proving x^x=4?

The main issue with proving x^x=4 is that there are multiple solutions to this equation. This means that there is not just one correct answer, making it more challenging to prove.

What are the different solutions to x^x=4?

There are three possible solutions to this equation: x = 2, x = 1.7725, and x = -0.7725. Each of these values satisfies the equation, but they are not the only solutions.

How can I prove that x^x=4 for a specific value of x?

To prove that x^x=4 for a specific value of x, you can use algebraic manipulation and substitution. For example, if you want to prove x^x=4 for x = 2, you can substitute 2 for x in the equation and show that it satisfies the equation.

Why is this problem considered a brain teaser?

This problem is considered a brain teaser because it requires creative thinking and multiple approaches to solve. It also challenges traditional mathematical methods and requires out-of-the-box thinking.

What are some real-life applications of this equation?

The equation x^x=4 has various real-life applications, such as in calculating growth rates in biology, determining optimal interest rates in economics, and solving optimization problems in engineering. It is also used in cryptography and coding theory to generate secure encryption keys.

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