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About river_rat

  • Birthday 07/21/1983

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  • Location
    South Africa
  • Interests
    DnD, M:TG, reading, music
  • College Major/Degree
  • Favorite Area of Science
    Semigroup Topologies
  • Occupation
    Teaching Assistant


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  1. You cannot find the roots of a general polynomial of degree [math] \geq 5 [/math] if you limit yourself to addition, multiplication and taking square roots Atheist. I guess that is what you meant by analytical, as there are other analytical solutions if you allow other operations and functions, like the elliptic functions for the quintic case.
  2. I'm surprised no one chastised me for my solution - oh well
  3. Hi abskebabs Here is a big hint for you - how do you factor [math] a^n - b^n [/math]?
  4. Hey abskebabs You can do one better then what you have posted so far: if [math] 2^n - 1[/math] is a prime number then [math]n[/math] must be prime. I'll leave the proof up to you, its not difficult
  5. The problem is impossible to solve - Dr Math has a nice solution http://mathforum.org/dr.math/faq/faq.3utilities.html
  6. or if you feel daring, your answer is [math] \Im \left( \int e^{(2+3i) x} dx \right) [/math] which saves you all the product rule pain PS [math] \Im [/math] denotes the imaginary part if you are wondering. The [math] dx [/math] is called a differential form (or one form in this case) and the theory here is quite interesting. It takes a surprising amount of mathematical work to get something that is more meaningful then the nonsense idea of an infinitely small but non-zero change in x.
  7. I would suggest "Probability and Random Processes", by Grimmett I think, for a quick and easy intro to the basics here. Its nice, starting with the basics and ending with the Ito calculus.
  8. How is the second recurrence well defined tree?
  9. Ah, but that is a different question. I only stated i could extend the algebraic operation of addition to a larger set that includes some ideal points. To start talking about limits you must have introduced a topology. To talk about limits and addition it would be nice if addition was continuous with respect to this topology. Now if you want a "nice" topological extension of the reals i would have to suggest the Stone-Cech compactification where addition can be extended by the universal property of that compactification. Sadly I think we only get an operator which is left continuous but we are still better equipped to talk about limits here. Well share the sketch
  10. But you have not explained why we are limited to group operations. Lets change the story a bit, we needed a way of talking about [math]\infty[/math] and addition on the naturals for this whole setup to work for the problem at hand. Now addition is not a group operation on the set of natural numbers but we have a perfectly legitimate semigroup operation which extends addition to the set [math]\mathbb{N} \cup \{ \infty \}[/math]. Just treat the added point as a zero under addition (i.e. [math] x + \infty = \infty + x = \infty[/math] [math]\forall x \in \mathbb{N} \cup \{ \infty \}[/math])
  11. Ok, reread what you replied to again and i still can't see your connection.
  12. Why didn't you use Ito's formula?
  13. Hi w=f[z] I got those solutions by just kicking out the equations for Marconi, Stern and Davison and solving the resulting system and then by kicking out the equations for Marconi, Stern and Cherenkov and solving the resulting linear system.
  14. Lol, this one is actually easy : just read the numbers out loud First Line : You have One One = Second Line Second Line : You have Two Ones = Third Line Third Line : You have One Two and One One = 4th Line 4th Line : You have One One and One Two and Two Ones = 5th Line 5th Line = You have Three Ones, Two Two's and One One so the next line is 312211
  15. Gogo, can you show me how you got that SDE from my suggested substitution?
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