Help Needed: Discrete Question on O(xⁿ)

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In summary, the conversation is about finding the least natural number n in order for √(x² + x³ + 3) to be O(xⁿ). The speaker is having trouble understanding the concept of "O" and is seeking help. They mention being able to determine n in simpler cases, but not knowing how to approach a polynomial. They also provide a link to an example of using "O" with polynomials. The conversation ends with a question about the purpose of finding a root and the speaker asks for clarification on the expression √(x² + x³ + 3)/xⁿ.
  • #1
hain
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I'm having some trouble with this discrete question:

Find the least natural number n such that
√(x² + x³ + 3) is O(xⁿ).

With the value of n that you have found, is it true that
xⁿ is O( √(x² + x³ + 3) )?


Can anyone help?
 
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  • #2
Well, starting with the definition of "O" would be a good idea. What is it?
 
  • #3
  • #4
These are easy: they're close enough to polynomials for the purposes asymptotic analysis. How would you do it if it was a polynomial?
 
  • #6
Why would you want to find a root? What is
[tex]\frac{\sqrt{x^2+x^3+ 3}}{x^n}[/tex]
?
 

1. What does O(xⁿ) mean in discrete mathematics?

O(xⁿ) is a mathematical notation used to represent the order or complexity of an algorithm. It indicates that the algorithm has a worst-case time complexity of O(xⁿ), meaning that the time it takes to run the algorithm increases exponentially as the input size increases.

2. How is O(xⁿ) different from other notations like O(1) or O(n)?

O(xⁿ) is different from other notations because it represents an exponential time complexity, while O(1) and O(n) represent constant and linear time complexities, respectively. This means that as the input size increases, the time it takes to run an algorithm with an O(xⁿ) complexity will increase much faster than an algorithm with an O(1) or O(n) complexity.

3. Can you give an example of an algorithm with an O(xⁿ) time complexity?

An example of an algorithm with an O(xⁿ) complexity is the recursive Fibonacci sequence algorithm. As the input number increases, the time it takes to calculate the corresponding Fibonacci number increases exponentially.

4. How can O(xⁿ) be used in analyzing the efficiency of algorithms?

O(xⁿ) is used to analyze the worst-case time complexity of an algorithm, which helps determine how efficient or scalable the algorithm is. By knowing the time complexity, we can make informed decisions about which algorithm to use for a particular problem based on the input size.

5. Is it possible for an algorithm to have a time complexity of O(xⁿ) in the best case scenario?

No, it is not possible for an algorithm to have a time complexity of O(xⁿ) in the best-case scenario. The best-case scenario for an algorithm is usually represented by O(1) or O(n), as the algorithm would have constant or linear time complexity in this case.

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